Assertions

Trait that contains ScalaTest's basic assertion methods.

You can use the assertions provided by this trait in any ScalaTest Suite, because Suite mixes in this trait. This trait is designed to be used independently of anything else in ScalaTest, though, so you can mix it into anything. (You can alternatively import the methods defined in this trait. For details, see the documentation for the Assertions companion object.

In any Scala program, you can write assertions by invoking assert and passing in a Boolean expression, such as:

val left = 2
val right = 1
assert(left == right)

If the passed expression is true, assert will return normally. If false, Scala's assert will complete abruptly with an AssertionError. This behavior is provided by the assert method defined in object Predef, whose members are implicitly imported into every Scala source file. This Assertions trait defines another assert method that hides the one in Predef. It behaves the same, except that if false is passed it throws TestFailedException instead of AssertionError. Why? Because unlike AssertionError, TestFailedException carries information about exactly which item in the stack trace represents the line of test code that failed, which can help users more quickly find an offending line of code in a failing test. In addition, ScalaTest's assert provides better error messages than Scala's assert.

If you pass the previous Boolean expression, left == right to assert in a ScalaTest test, a failure will be reported that, because assert is implemented as a macro, includes reporting the left and right values. For example, given the same code as above but using ScalaTest assertions:

import org.scalatest.Assertions._
val left = 2
val right = 1
assert(left == right)

The detail message in the thrown TestFailedException from this assert will be: "2 did not equal 1".

ScalaTest's assert macro works by recognizing patterns in the AST of the expression passed to assert and, for a finite set of common expressions, giving an error message that an equivalent ScalaTest matcher expression would give. Here are some examples, where a is 1, b is 2, c is 3, d is 4, xs is List(a, b, c), and num is 1.0:

assert(a == b || c >= d)
// Error message: 1 did not equal 2, and 3 was not greater than or equal to 4

assert(xs.exists(_ == 4))
// Error message: List(1, 2, 3) did not contain 4

assert("hello".startsWith("h") && "goodbye".endsWith("y"))
// Error message: "hello" started with "h", but "goodbye" did not end with "y"

assert(num.isInstanceOf[Int])
// Error message: 1.0 was not instance of scala.Int

assert(Some(2).isEmpty)
// Error message: Some(2) was not empty

For expressions that are not recognized, the macro currently prints out a string representation of the (desugared) AST and adds "was false". Here are some examples of error messages for unrecognized expressions:

assert(None.isDefined)
// Error message: scala.None.isDefined was false

assert(xs.exists(i => i > 10))
// Error message: xs.exists(((i: Int) => i.>(10))) was false

You can augment the standard error message by providing a String as a second argument to assert, like this:

val attempted = 2
assert(attempted == 1, "Execution was attempted " + left + " times instead of 1 time")

Using this form of assert, the failure report will be more specific to your problem domain, thereby helping you debug the problem. This Assertions trait also mixes in the TripleEquals, which gives you a === operator that allows you to customize Equality, perform equality checks with numeric Tolerance, and enforce type constraints at compile time with sibling traits TypeCheckedTripleEquals and ConversionCheckedTripleEquals.

Expected results

Although the assert macro provides a natural, readable extension to Scala's assert mechanism that provides good error messages, as the operands become lengthy, the code becomes less readable. In addition, the error messages generated for == and === comparisons don't distinguish between actual and expected values. The operands are just called left and right, because if one were named expected and the other actual, it would be difficult for people to remember which was which. To help with these limitations of assertions, Suite includes a method called assertResult that can be used as an alternative to assert. To use assertResult, you place the expected value in parentheses after assertResult, followed by curly braces containing code that should result in the expected value. For example:

val a = 5
val b = 2
assertResult(2) {
  a - b
}

In this case, the expected value is 2, and the code being tested is a - b. This assertion will fail, and the detail message in the TestFailedException will read, "Expected 2, but got 3."

Forcing failures

If you just need the test to fail, you can write:

fail()

Or, if you want the test to fail with a message, write:

fail("I've got a bad feeling about this")

Achieving success

In async style tests, you must end your test body with either Future[Assertion] or Assertion. ScalaTest's assertions (including matcher expressions) have result type Assertion, so ending with an assertion will satisfy the compiler. If a test body or function body passed to Future.map does not end with type Assertion, however, you can fix the type error by placing succeed at the end of the test or function body:

succeed // Has type Assertion

Expected exceptions

Sometimes you need to test whether a method throws an expected exception under certain circumstances, such as when invalid arguments are passed to the method. You can do this in the JUnit 3 style, like this:

val s = "hi"
try {
  s.charAt(-1)
  fail()
}
catch {
  case _: IndexOutOfBoundsException => // Expected, so continue
}

If charAt throws IndexOutOfBoundsException as expected, control will transfer to the catch case, which does nothing. If, however, charAt fails to throw an exception, the next statement, fail(), will be run. The fail method always completes abruptly with a TestFailedException, thereby signaling a failed test.

To make this common use case easier to express and read, ScalaTest provides two methods: assertThrows and intercept. Here's how you use assertThrows:

val s = "hi"
assertThrows[IndexOutOfBoundsException] { // Result type: Assertion
  s.charAt(-1)
}

This code behaves much like the previous example. If charAt throws an instance of IndexOutOfBoundsException, assertThrows will return Succeeded. But if charAt completes normally, or throws a different exception, assertThrows will complete abruptly with a TestFailedException.

The intercept method behaves the same as assertThrows, except that instead of returning Succeeded, intercept returns the caught exception so that you can inspect it further if you wish. For example, you may need to ensure that data contained inside the exception have expected values. Here's an example:

val s = "hi"
val caught =
  intercept[IndexOutOfBoundsException] { // Result type: IndexOutOfBoundsException
    s.charAt(-1)
  }
assert(caught.getMessage.indexOf("-1") != -1)

Checking that a snippet of code does or does not compile

Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest's Assertions trait includes the following syntax for that purpose:

assertDoesNotCompile("val a: String = 1")

If you want to ensure that a snippet of code does not compile because of a type error (as opposed to a syntax error), use:

assertTypeError("val a: String = 1")

Note that the assertTypeError call will only succeed if the given snippet of code does not compile because of a type error. A syntax error will still result on a thrown TestFailedException.

If you want to state that a snippet of code does compile, you can make that more obvious with:

assertCompiles("val a: Int = 1")

Although the previous three constructs are implemented with macros that determine at compile time whether the snippet of code represented by the string does or does not compile, errors are reported as test failures at runtime.

Assumptions

Trait Assertions also provides methods that allow you to cancel a test. You would cancel a test if a resource required by the test was unavailable. For example, if a test requires an external database to be online, and it isn't, the test could be canceled to indicate it was unable to run because of the missing database. Such a test assumes a database is available, and you can use the assume method to indicate this at the beginning of the test, like this:

assume(database.isAvailable)

For each overloaded assert method, trait Assertions provides an overloaded assume method with an identical signature and behavior, except the assume methods throw TestCanceledException whereas the assert methods throw TestFailedException. As with assert, assume hides a Scala method in Predef that performs a similar function, but throws AssertionError. And just as you can with assert, you will get an error message extracted by a macro from the AST passed to assume, and can optionally provide a clue string to augment this error message. Here are some examples:

assume(database.isAvailable, "The database was down again")
assume(database.getAllUsers.count === 9)

Forcing cancelations

For each overloaded fail method, there's a corresponding cancel method with an identical signature and behavior, except the cancel methods throw TestCanceledException whereas the fail methods throw TestFailedException. Thus if you just need to cancel a test, you can write:

cancel()

If you want to cancel the test with a message, just place the message in the parentheses:

cancel("Can't run the test because no internet connection was found")

Getting a clue

If you want more information that is provided by default by the methods if this trait, you can supply a "clue" string in one of several ways. The extra information (or "clues") you provide will be included in the detail message of the thrown exception. Both assert and assertResult provide a way for a clue to be included directly, intercept does not. Here's an example of clues provided directly in assert:

assert(1 + 1 === 3, "this is a clue")

and in assertResult:

assertResult(3, "this is a clue") { 1 + 1 }

The exceptions thrown by the previous two statements will include the clue string, "this is a clue", in the exception's detail message. To get the same clue in the detail message of an exception thrown by a failed intercept call requires using withClue:

withClue("this is a clue") {
  intercept[IndexOutOfBoundsException] {
    "hi".charAt(-1)
  }
}

The withClue method will only prepend the clue string to the detail message of exception types that mix in the ModifiableMessage trait. See the documentation for ModifiableMessage for more information. If you wish to place a clue string after a block of code, see the documentation for AppendedClues.

Note: ScalaTest's assertTypeError construct is in part inspired by the illTyped macro of shapeless.

Source: Assertions.scala

Linear Supertypes

TripleEquals, TripleEqualsSupport, AnyRef, Any

Known Subclasses

Assertions, AssertionsForJUnit, AssertionsForJUnit, AsyncFeatureSpec, AsyncFeatureSpec, AsyncFeatureSpecLike, AsyncFeatureSpecLike, AsyncFlatSpec, AsyncFlatSpec, AsyncFlatSpecLike, AsyncFlatSpecLike, AsyncFreeSpec, AsyncFreeSpec, AsyncFreeSpecLike, AsyncFreeSpecLike, AsyncFunSpec, AsyncFunSpec, AsyncFunSpecLike, AsyncFunSpecLike, AsyncFunSuite, AsyncFunSuite, AsyncFunSuiteLike, AsyncFunSuiteLike, AsyncTestSuite, AsyncTestSuite, AsyncWordSpec, AsyncWordSpec, AsyncWordSpecLike, AsyncWordSpecLike, ConfigMapWrapperSuite, DiagrammedAssertions, DiagrammedAssertions, FeatureSpec, FeatureSpec, FeatureSpecLike, FeatureSpecLike, FlatSpec, FlatSpec, FlatSpecLike, FlatSpecLike, FreeSpec, FreeSpec, FreeSpec, FreeSpecLike, FreeSpecLike, FreeSpecLike, FunSpec, FunSpec, FunSpec, FunSpecLike, FunSpecLike, FunSpecLike, FunSuite, FunSuite, FunSuiteLike, FunSuiteLike, JUnit3Suite, JUnitSuite, JUnitSuiteLike, JUnitWrapperSuite, Matchers, Matchers, MustMatchers, MustMatchers, NonImplicitAssertions, NonImplicitAssertions, PropSpec, PropSpec, PropSpecLike, PropSpecLike, RefSpec, RefSpecLike, Sequential, Spec, SpecLike, Stepwise, Suite, Suite, Suites, TestNGSuite, TestNGSuiteLike, TestNGWrapperSuite, TestSuite, TestSuite, WordSpec, WordSpec, WordSpecLike, WordSpecLike

Type Members

class AssertionsHelper extends AnyRef

Helper class used by code generated by the assert macro.
Helper class used by code generated by the assert macro.
class CheckingEqualizer[L] extends AnyRef

Definition Classes
TripleEqualsSupport
class Equalizer[L] extends AnyRef

Definition Classes
TripleEqualsSupport

Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def !==[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

Definition Classes
TripleEqualsSupport
def !==(right: Null): TripleEqualsInvocation[Null]

Definition Classes
TripleEqualsSupport
def !==[T](right: T): TripleEqualsInvocation[T]

Definition Classes
TripleEqualsSupport
final def ##(): Int

Definition Classes
AnyRef → Any
final def ==(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def ===[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

Definition Classes
TripleEqualsSupport
def ===(right: Null): TripleEqualsInvocation[Null]

Definition Classes
TripleEqualsSupport
def ===[T](right: T): TripleEqualsInvocation[T]

Definition Classes
TripleEqualsSupport
final def asInstanceOf[T0]: T0

Definition Classes
Any
macro def assert(condition: Boolean, clue: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

Assert that a boolean condition, described in String message, is true.
Assert that a boolean condition, described in String message, is true. If the condition is true, this method returns normally. Else, it throws TestFailedException with a helpful error message appended with the String obtained by invoking toString on the specified clue as the exception's detail message.
This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:
- assert(a == b, "a good clue")
- assert(a != b, "a good clue")
- assert(a === b, "a good clue")
- assert(a !== b, "a good clue")
- assert(a > b, "a good clue")
- assert(a >= b, "a good clue")
- assert(a < b, "a good clue")
- assert(a <= b, "a good clue")
- assert(a startsWith "prefix", "a good clue")
- assert(a endsWith "postfix", "a good clue")
- assert(a contains "something", "a good clue")
- assert(a eq b, "a good clue")
- assert(a ne b, "a good clue")
- assert(a > 0 && b > 5, "a good clue")
- assert(a > 0 || b > 5, "a good clue")
- assert(a.isEmpty, "a good clue")
- assert(!a.isEmpty, "a good clue")
- assert(a.isInstanceOf[String], "a good clue")
- assert(a.length == 8, "a good clue")
- assert(a.size == 8, "a good clue")
- assert(a.exists(_ == 8), "a good clue")
At this time, any other form of expression will just get a TestFailedException with message saying the given expression was false. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean to be the default in tests. This makes === consistent between tests and production code.
condition
the boolean condition to assert
clue
An objects whose toString method returns a message to include in a failure report.

Exceptions thrown
NullArgumentException if message is null.
TestFailedException if the condition is false.
macro def assert(condition: Boolean)(implicit prettifier: Prettifier, pos: Position): Assertion

Assert that a boolean condition is true.
Assert that a boolean condition is true. If the condition is true, this method returns normally. Else, it throws TestFailedException.
This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:
- assert(a == b)
- assert(a != b)
- assert(a === b)
- assert(a !== b)
- assert(a > b)
- assert(a >= b)
- assert(a < b)
- assert(a <= b)
- assert(a startsWith "prefix")
- assert(a endsWith "postfix")
- assert(a contains "something")
- assert(a eq b)
- assert(a ne b)
- assert(a > 0 && b > 5)
- assert(a > 0 || b > 5)
- assert(a.isEmpty)
- assert(!a.isEmpty)
- assert(a.isInstanceOf[String])
- assert(a.length == 8)
- assert(a.size == 8)
- assert(a.exists(_ == 8))
At this time, any other form of expression will get a TestFailedException with message saying the given expression was false. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean to be the default in tests. This makes === consistent between tests and production code.
condition
the boolean condition to assert

Exceptions thrown
TestFailedException if the condition is false.
macro def assertCompiles(code: String)(implicit pos: Position): Assertion

Asserts that a given string snippet of code passes both the Scala parser and type checker.
Asserts that a given string snippet of code passes both the Scala parser and type checker.
You can use this to make sure a snippet of code compiles:
```
assertCompiles("val a: Int = 1")
```
Although assertCompiles is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string compiles, errors (i.e., snippets of code that do not compile) are reported as test failures at runtime.
code
the snippet of code that should compile
macro def assertDoesNotCompile(code: String)(implicit pos: Position): Assertion

Asserts that a given string snippet of code does not pass either the Scala parser or type checker.
Asserts that a given string snippet of code does not pass either the Scala parser or type checker.
Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest's Assertions trait includes the following syntax for that purpose:
```
assertDoesNotCompile("val a: String = \"a string")
```
Although assertDoesNotCompile is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string doesn't compile, errors (i.e., snippets of code that do compile) are reported as test failures at runtime.
Note that the difference between assertTypeError and assertDoesNotCompile is that assertDoesNotCompile will succeed if the given code does not compile for any reason, whereas assertTypeError will only succeed if the given code does not compile because of a type error. If the given code does not compile because of a syntax error, for example, assertDoesNotCompile will return normally but assertTypeError will throw a TestFailedException.
code
the snippet of code that should not type check
def assertResult(expected: Any)(actual: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

Assert that the value passed as expected equals the value passed as actual.
Assert that the value passed as expected equals the value passed as actual. If the actual value equals the expected value (as determined by ==), assertResult returns normally. Else, assertResult throws a TestFailedException whose detail message includes the expected and actual values.
expected
the expected value
actual
the actual value, which should equal the passed expected value

Exceptions thrown
TestFailedException if the passed actual value does not equal the passed expected value.
def assertResult(expected: Any, clue: Any)(actual: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

Assert that the value passed as expected equals the value passed as actual.
Assert that the value passed as expected equals the value passed as actual. If the actual equals the expected (as determined by ==), assertResult returns normally. Else, if actual is not equal to expected, assertResult throws a TestFailedException whose detail message includes the expected and actual values, as well as the String obtained by invoking toString on the passed clue.
expected
the expected value
clue
An object whose toString method returns a message to include in a failure report.
actual
the actual value, which should equal the passed expected value

Exceptions thrown
TestFailedException if the passed actual value does not equal the passed expected value.
def assertThrows[T <: AnyRef](f: ⇒ Any)(implicit classTag: ClassTag[T], pos: Position): Assertion

Ensure that an expected exception is thrown by the passed function value.
Ensure that an expected exception is thrown by the passed function value. The thrown exception must be an instance of the type specified by the type parameter of this method. This method invokes the passed function. If the function throws an exception that's an instance of the specified type, this method returns Succeeded. Else, whether the passed function returns normally or completes abruptly with a different exception, this method throws TestFailedException.
Note that the type specified as this method's type parameter may represent any subtype of AnyRef, not just Throwable or one of its subclasses. In Scala, exceptions can be caught based on traits they implement, so it may at times make sense to specify a trait that the intercepted exception's class must mix in. If a class instance is passed for a type that could not possibly be used to catch an exception (such as String, for example), this method will complete abruptly with a TestFailedException.
Also note that the difference between this method and intercept is that this method does not return the expected exception, so it does not let you perform further assertions on that exception. Instead, this method returns Succeeded, which means it can serve as the last statement in an async- or safe-style suite. It also indicates to the reader of the code that nothing further is expected about the thrown exception other than its type. The recommended usage is to use assertThrows by default, intercept only when you need to inspect the caught exception further.
f
the function value that should throw the expected exception
classTag
an implicit ClassTag representing the type of the specified type parameter.
returns
the Succeeded singleton, if an exception of the expected type is thrown

Exceptions thrown
TestFailedException if the passed function does not complete abruptly with an exception that's an instance of the specified type.
macro def assertTypeError(code: String)(implicit pos: Position): Assertion

Asserts that a given string snippet of code does not pass the Scala type checker, failing if the given snippet does not pass the Scala parser.
Asserts that a given string snippet of code does not pass the Scala type checker, failing if the given snippet does not pass the Scala parser.
Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest's Assertions trait includes the following syntax for that purpose:
```
assertTypeError("val a: String = 1")
```
Although assertTypeError is implemented with a macro that determines at compile time whether the snippet of code represented by the passed string type checks, errors (i.e., snippets of code that do type check) are reported as test failures at runtime.
Note that the difference between assertTypeError and assertDoesNotCompile is that assertDoesNotCompile will succeed if the given code does not compile for any reason, whereas assertTypeError will only succeed if the given code does not compile because of a type error. If the given code does not compile because of a syntax error, for example, assertDoesNotCompile will return normally but assertTypeError will throw a TestFailedException.
code
the snippet of code that should not type check
val assertionsHelper: AssertionsHelper

Helper instance used by code generated by macro assertion.
macro def assume(condition: Boolean, clue: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

Assume that a boolean condition, described in String message, is true.
Assume that a boolean condition, described in String message, is true. If the condition is true, this method returns normally. Else, it throws TestCanceledException with a helpful error message appended with String obtained by invoking toString on the specified clue as the exception's detail message.
This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:
- assume(a == b, "a good clue")
- assume(a != b, "a good clue")
- assume(a === b, "a good clue")
- assume(a !== b, "a good clue")
- assume(a > b, "a good clue")
- assume(a >= b, "a good clue")
- assume(a < b, "a good clue")
- assume(a <= b, "a good clue")
- assume(a startsWith "prefix", "a good clue")
- assume(a endsWith "postfix", "a good clue")
- assume(a contains "something", "a good clue")
- assume(a eq b, "a good clue")
- assume(a ne b, "a good clue")
- assume(a > 0 && b > 5, "a good clue")
- assume(a > 0 || b > 5, "a good clue")
- assume(a.isEmpty, "a good clue")
- assume(!a.isEmpty, "a good clue")
- assume(a.isInstanceOf[String], "a good clue")
- assume(a.length == 8, "a good clue")
- assume(a.size == 8, "a good clue")
- assume(a.exists(_ == 8), "a good clue")
At this time, any other form of expression will just get a TestCanceledException with message saying the given expression was false. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean to be the default in tests. This makes === consistent between tests and production code.
condition
the boolean condition to assume
clue
An objects whose toString method returns a message to include in a failure report.

Exceptions thrown
NullArgumentException if message is null.
TestCanceledException if the condition is false.
macro def assume(condition: Boolean)(implicit prettifier: Prettifier, pos: Position): Assertion

Assume that a boolean condition is true.
Assume that a boolean condition is true. If the condition is true, this method returns normally. Else, it throws TestCanceledException.
This method is implemented in terms of a Scala macro that will generate a more helpful error message for expressions of this form:
- assume(a == b)
- assume(a != b)
- assume(a === b)
- assume(a !== b)
- assume(a > b)
- assume(a >= b)
- assume(a < b)
- assume(a <= b)
- assume(a startsWith "prefix")
- assume(a endsWith "postfix")
- assume(a contains "something")
- assume(a eq b)
- assume(a ne b)
- assume(a > 0 && b > 5)
- assume(a > 0 || b > 5)
- assume(a.isEmpty)
- assume(!a.isEmpty)
- assume(a.isInstanceOf[String])
- assume(a.length == 8)
- assume(a.size == 8)
- assume(a.exists(_ == 8))
At this time, any other form of expression will just get a TestCanceledException with message saying the given expression was false. In the future, we will enhance this macro to give helpful error messages in more situations. In ScalaTest 2.0, however, this behavior was sufficient to allow the === that returns Boolean to be the default in tests. This makes === consistent between tests and production code.
condition
the boolean condition to assume

Exceptions thrown
TestCanceledException if the condition is false.
def cancel(cause: Throwable)(implicit pos: Position): Nothing

Throws TestCanceledException, with the passed Throwable cause, to indicate a test failed.
Throws TestCanceledException, with the passed Throwable cause, to indicate a test failed. The getMessage method of the thrown TestCanceledException will return cause.toString.
cause
a Throwable that indicates the cause of the cancellation.

Exceptions thrown
NullArgumentException if cause is null
def cancel(message: String, cause: Throwable)(implicit pos: Position): Nothing

Throws TestCanceledException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
Throws TestCanceledException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
message
A message describing the failure.
cause
A Throwable that indicates the cause of the failure.

Exceptions thrown
NullArgumentException if message or cause is null
def cancel(message: String)(implicit pos: Position): Nothing

Throws TestCanceledException, with the passed String message as the exception's detail message, to indicate a test was canceled.
Throws TestCanceledException, with the passed String message as the exception's detail message, to indicate a test was canceled.
message
A message describing the cancellation.

Exceptions thrown
NullArgumentException if message is null
def cancel()(implicit pos: Position): Nothing

Throws TestCanceledException to indicate a test was canceled.
Throws TestCanceledException to indicate a test was canceled.
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( ... )
def conversionCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], cnv: (B) ⇒ A): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToAToBConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: <:<[A, B]): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToAToBConversionConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: (A) ⇒ B): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToBToAConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: <:<[B, A]): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
def convertEquivalenceToBToAConversionConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: (B) ⇒ A): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
def convertToCheckingEqualizer[T](left: T): CheckingEqualizer[T]

Definition Classes
TripleEquals → TripleEqualsSupport
implicit def convertToEqualizer[T](left: T): Equalizer[T]

Definition Classes
TripleEquals → TripleEqualsSupport
def defaultEquality[A]: Equality[A]

Definition Classes
TripleEqualsSupport
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
def equals(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def fail(cause: Throwable)(implicit pos: Position): Nothing

Throws TestFailedException, with the passed Throwable cause, to indicate a test failed.
Throws TestFailedException, with the passed Throwable cause, to indicate a test failed. The getMessage method of the thrown TestFailedException will return cause.toString.
cause
a Throwable that indicates the cause of the failure.

Exceptions thrown
NullArgumentException if cause is null
def fail(message: String, cause: Throwable)(implicit pos: Position): Nothing

Throws TestFailedException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
Throws TestFailedException, with the passed String message as the exception's detail message and Throwable cause, to indicate a test failed.
message
A message describing the failure.
cause
A Throwable that indicates the cause of the failure.

Exceptions thrown
NullArgumentException if message or cause is null
def fail(message: String)(implicit pos: Position): Nothing

Throws TestFailedException, with the passed String message as the exception's detail message, to indicate a test failed.
Throws TestFailedException, with the passed String message as the exception's detail message, to indicate a test failed.
message
A message describing the failure.

Exceptions thrown
NullArgumentException if message is null
def fail()(implicit pos: Position): Nothing

Throws TestFailedException to indicate a test failed.
Throws TestFailedException to indicate a test failed.
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
def hashCode(): Int

Definition Classes
AnyRef → Any
def intercept[T <: AnyRef](f: ⇒ Any)(implicit classTag: ClassTag[T], pos: Position): T

Intercept and return an exception that's expected to be thrown by the passed function value.
Intercept and return an exception that's expected to be thrown by the passed function value. The thrown exception must be an instance of the type specified by the type parameter of this method. This method invokes the passed function. If the function throws an exception that's an instance of the specified type, this method returns that exception. Else, whether the passed function returns normally or completes abruptly with a different exception, this method throws TestFailedException.
Note that the type specified as this method's type parameter may represent any subtype of AnyRef, not just Throwable or one of its subclasses. In Scala, exceptions can be caught based on traits they implement, so it may at times make sense to specify a trait that the intercepted exception's class must mix in. If a class instance is passed for a type that could not possibly be used to catch an exception (such as String, for example), this method will complete abruptly with a TestFailedException.
Also note that the difference between this method and assertThrows is that this method returns the expected exception, so it lets you perform further assertions on that exception. By contrast, the assertThrows method returns Succeeded, which means it can serve as the last statement in an async- or safe-style suite. assertThrows also indicates to the reader of the code that nothing further is expected about the thrown exception other than its type. The recommended usage is to use assertThrows by default, intercept only when you need to inspect the caught exception further.
f
the function value that should throw the expected exception
classTag
an implicit ClassTag representing the type of the specified type parameter.
returns
the intercepted exception, if it is of the expected type

Exceptions thrown
TestFailedException if the passed function does not complete abruptly with an exception that's an instance of the specified type.
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
def lowPriorityConversionCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], cnv: (A) ⇒ B): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
def lowPriorityTypeCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], ev: <:<[A, B]): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
final def notifyAll(): Unit

Definition Classes
AnyRef
def pending: Assertion with PendingStatement

Throws TestPendingException to indicate a test is pending.
Throws TestPendingException to indicate a test is pending.
A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, the before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later.
To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality it is intended to test, has not yet been implemented.
Note: This method always completes abruptly with a TestPendingException. Thus it always has a side effect. Methods with side effects are usually invoked with parentheses, as in pending(). This method is defined as a parameterless method, in flagrant contradiction to recommended Scala style, because it forms a kind of DSL for pending tests. It enables tests in suites such as FunSuite or FunSpec to be denoted by placing "(pending)" after the test name, as in:
```
test("that style rules are not laws") (pending)
```
Readers of the code see "pending" in parentheses, which looks like a little note attached to the test name to indicate it is pending. Whereas "(pending()) looks more like a method call, "(pending)" lets readers stay at a higher level, forgetting how it is implemented and just focusing on the intent of the programmer who wrote the code.
def pendingUntilFixed(f: ⇒ Unit)(implicit pos: Position): Assertion with PendingStatement

Execute the passed block of code, and if it completes abruptly, throw TestPendingException, else throw TestFailedException.
Execute the passed block of code, and if it completes abruptly, throw TestPendingException, else throw TestFailedException.
This method can be used to temporarily change a failing test into a pending test in such a way that it will automatically turn back into a failing test once the problem originally causing the test to fail has been fixed. At that point, you need only remove the pendingUntilFixed call. In other words, a pendingUntilFixed surrounding a block of code that isn't broken is treated as a test failure. The motivation for this behavior is to encourage people to remove pendingUntilFixed calls when there are no longer needed.
This method facilitates a style of testing in which tests are written before the code they test. Sometimes you may encounter a test failure that requires more functionality than you want to tackle without writing more tests. In this case you can mark the bit of test code causing the failure with pendingUntilFixed. You can then write more tests and functionality that eventually will get your production code to a point where the original test won't fail anymore. At this point the code block marked with pendingUntilFixed will no longer throw an exception (because the problem has been fixed). This will in turn cause pendingUntilFixed to throw TestFailedException with a detail message explaining you need to go back and remove the pendingUntilFixed call as the problem orginally causing your test code to fail has been fixed.
f
a block of code, which if it completes abruptly, should trigger a TestPendingException

Exceptions thrown
TestPendingException if the passed block of code completes abruptly with an Exception or AssertionError
final val succeed: Assertion

The Succeeded singleton.
The Succeeded singleton.
You can use succeed to solve a type error when an async test does not end in either Future[Assertion] or Assertion. Because Assertion is a type alias for Succeeded.type, putting succeed at the end of a test body (or at the end of a function being used to map the final future of a test body) will solve the type error.
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String

Definition Classes
AnyRef → Any
def typeCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], ev: <:<[B, A]): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
implicit def unconstrainedEquality[A, B](implicit equalityOfA: Equality[A]): CanEqual[A, B]

Definition Classes
TripleEquals → TripleEqualsSupport
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
def withClue[T](clue: Any)(fun: ⇒ T): T

Executes the block of code passed as the second parameter, and, if it completes abruptly with a ModifiableMessage exception, prepends the "clue" string passed as the first parameter to the beginning of the detail message of that thrown exception, then rethrows it.
Executes the block of code passed as the second parameter, and, if it completes abruptly with a ModifiableMessage exception, prepends the "clue" string passed as the first parameter to the beginning of the detail message of that thrown exception, then rethrows it. If clue does not end in a white space character, one space will be added between it and the existing detail message (unless the detail message is not defined).
This method allows you to add more information about what went wrong that will be reported when a test fails. Here's an example:
```
withClue("(Employee's name was: " + employee.name + ")") {
  intercept[IllegalArgumentException] {
    employee.getTask(-1)
  }
}
```
If an invocation of intercept completed abruptly with an exception, the resulting message would be something like:
```
(Employee's name was Bob Jones) Expected IllegalArgumentException to be thrown, but no exception was thrown
```
Exceptions thrown
NullArgumentException if the passed clue is null

Deprecated Value Members

def trap[T](f: ⇒ T): Throwable

Trap and return any thrown exception that would normally cause a ScalaTest test to fail, or create and return a new RuntimeException indicating no exception is thrown.

This method is intended to be used in the Scala interpreter to eliminate large stack traces when trying out ScalaTest assertions and matcher expressions. It is not intended to be used in regular test code. If you want to ensure that a bit of code throws an expected exception, use intercept, not trap. Here's an example interpreter session without trap:

scala> import org.scalatest._
import org.scalatest._

scala> import Matchers._
import Matchers._

scala> val x = 12
a: Int = 12

scala> x shouldEqual 13
org.scalatest.exceptions.TestFailedException: 12 did not equal 13
   at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:449)
   at org.scalatest.Assertions$.newAssertionFailedException(Assertions.scala:1203)
   at org.scalatest.Assertions$AssertionsHelper.macroAssertTrue(Assertions.scala:417)
   at .<init>(<console>:15)
   at .<clinit>(<console>)
   at .<init>(<console>:7)
   at .<clinit>(<console>)
   at $print(<console>)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
   at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:731)
   at scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:980)
   at scala.tools.nsc.interpreter.IMain.loadAndRunReq$1(IMain.scala:570)
   at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:601)
   at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:565)
   at scala.tools.nsc.interpreter.ILoop.reallyInterpret$1(ILoop.scala:745)
   at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:790)
   at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:702)
   at scala.tools.nsc.interpreter.ILoop.processLine$1(ILoop.scala:566)
   at scala.tools.nsc.interpreter.ILoop.innerLoop$1(ILoop.scala:573)
   at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:576)
   at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply$mcZ$sp(ILoop.scala:867)
   at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
   at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:822)
   at scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
   at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:822)
   at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:83)
   at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:96)
   at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:105)
   at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

That's a pretty tall stack trace. Here's what it looks like when you use trap:

scala> trap { x shouldEqual 13 }
res1: Throwable = org.scalatest.exceptions.TestFailedException: 12 did not equal 13

Much less clutter. Bear in mind, however, that if no exception is thrown by the passed block of code, the trap method will create a new NormalResult (a subclass of Throwable made for this purpose only) and return that. If the result was the Unit value, it will simply say that no exception was thrown:

scala> trap { x shouldEqual 12 }
res2: Throwable = No exception was thrown.

If the passed block of code results in a value other than Unit, the NormalResult's toString will print the value:

scala> trap { "Dude!" }
res3: Throwable = No exception was thrown. Instead, result was: "Dude!"

Although you can access the result value from the NormalResult, its type is Any and therefore not very convenient to use. It is not intended that trap be used in test code. The sole intended use case for trap is decluttering Scala interpreter sessions by eliminating stack traces when executing assertion and matcher expressions.

Annotations: @deprecated
Deprecated: The trap method is no longer needed for demos in the REPL, which now abreviates stack traces, and will be removed in a future version of ScalaTest

Related Docs: object Assertions | package scalatest

trait Assertions extends TripleEquals

Expected results

Forcing failures

Achieving success

Expected exceptions

Checking that a snippet of code does or does not compile

Assumptions

Forcing cancelations

Getting a clue

Type Members

class AssertionsHelper extends AnyRef

class CheckingEqualizer[L] extends AnyRef

class Equalizer[L] extends AnyRef

Value Members

final def !=(arg0: Any): Boolean

def !==[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

def !==(right: Null): TripleEqualsInvocation[Null]

def !==[T](right: T): TripleEqualsInvocation[T]

final def ##(): Int

final def ==(arg0: Any): Boolean

def ===[T](right: Spread[T]): TripleEqualsInvocationOnSpread[T]

def ===(right: Null): TripleEqualsInvocation[Null]

def ===[T](right: T): TripleEqualsInvocation[T]

final def asInstanceOf[T0]: T0

macro def assert(condition: Boolean, clue: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

macro def assert(condition: Boolean)(implicit prettifier: Prettifier, pos: Position): Assertion

macro def assertCompiles(code: String)(implicit pos: Position): Assertion

macro def assertDoesNotCompile(code: String)(implicit pos: Position): Assertion

def assertResult(expected: Any)(actual: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

def assertResult(expected: Any, clue: Any)(actual: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

def assertThrows[T <: AnyRef](f: ⇒ Any)(implicit classTag: ClassTag[T], pos: Position): Assertion

macro def assertTypeError(code: String)(implicit pos: Position): Assertion

val assertionsHelper: AssertionsHelper

macro def assume(condition: Boolean, clue: Any)(implicit prettifier: Prettifier, pos: Position): Assertion

macro def assume(condition: Boolean)(implicit prettifier: Prettifier, pos: Position): Assertion

def cancel(cause: Throwable)(implicit pos: Position): Nothing

def cancel(message: String, cause: Throwable)(implicit pos: Position): Nothing

def cancel(message: String)(implicit pos: Position): Nothing

def cancel()(implicit pos: Position): Nothing

def clone(): AnyRef

def conversionCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], cnv: (B) ⇒ A): CanEqual[A, B]

def convertEquivalenceToAToBConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: <:<[A, B]): CanEqual[A, B]

def convertEquivalenceToAToBConversionConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: (A) ⇒ B): CanEqual[A, B]

def convertEquivalenceToBToAConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: <:<[B, A]): CanEqual[A, B]

def convertEquivalenceToBToAConversionConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: (B) ⇒ A): CanEqual[A, B]

def convertToCheckingEqualizer[T](left: T): CheckingEqualizer[T]

implicit def convertToEqualizer[T](left: T): Equalizer[T]

def defaultEquality[A]: Equality[A]

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def fail(cause: Throwable)(implicit pos: Position): Nothing

def fail(message: String, cause: Throwable)(implicit pos: Position): Nothing

def fail(message: String)(implicit pos: Position): Nothing

def fail()(implicit pos: Position): Nothing

def finalize(): Unit

final def getClass(): Class[_]

def hashCode(): Int

def intercept[T <: AnyRef](f: ⇒ Any)(implicit classTag: ClassTag[T], pos: Position): T

final def isInstanceOf[T0]: Boolean

def lowPriorityConversionCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], cnv: (A) ⇒ B): CanEqual[A, B]

def lowPriorityTypeCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], ev: <:<[A, B]): CanEqual[A, B]

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

def pending: Assertion with PendingStatement

def pendingUntilFixed(f: ⇒ Unit)(implicit pos: Position): Assertion with PendingStatement

final val succeed: Assertion

final def synchronized[T0](arg0: ⇒ T0): T0

def toString(): String

def typeCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], ev: <:<[B, A]): CanEqual[A, B]

implicit def unconstrainedEquality[A, B](implicit equalityOfA: Equality[A]): CanEqual[A, B]

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

def withClue[T](clue: Any)(fun: ⇒ T): T

Deprecated Value Members

def trap[T](f: ⇒ T): Throwable

Inherited from TripleEquals