Package com.google.common.truth

Class Subject

java.lang.Object
com.google.common.truth.Subject
Direct Known Subclasses:
AbstractArraySubject, BooleanSubject, ClassSubject, ComparableSubject, GuavaOptionalSubject, IntStreamSubject, IterableSubject, LongStreamSubject, MapSubject, MultimapSubject, OptionalDoubleSubject, OptionalIntSubject, OptionalLongSubject, OptionalSubject, PathSubject, StreamSubject, TableSubject, ThrowableSubject
public class Subject extends Object
An object that lets you perform checks on the value under test. For example, Subject contains isEqualTo(Object) and isInstanceOf(Class), and StringSubject contains startsWith(String).

To create a Subject instance, most users will call an assertThat method. For information about other ways to create an instance, see this FAQ entry.

For people extending Truth

For information about writing a custom Subject, see our doc on extensions.

  • Field Details

    • IGNORE_STRATEGY

      private static final FailureStrategy IGNORE_STRATEGY

    • metadata

      private final FailureMetadata metadata

    • actual

      private final Object actual

    • customName

      private String customName

    • typeDescriptionOverride

      private final String typeDescriptionOverride

    • hexDigits

      private static final char[] hexDigits

    • STRINGIFY

      private static final com.google.common.base.Function<Object,Object> STRINGIFY

    • HEX_DIGITS

      private static final char[] HEX_DIGITS

  • Constructor Details

    • Subject

      protected Subject(FailureMetadata metadata, Object actual)
      Constructor for use by subclasses. If you want to create an instance of this class itself, call check(...).that(actual).

    • Subject

      Subject(FailureMetadata metadata, Object actual, String typeDescriptionOverride)
      Special constructor that lets subclasses provide a description of the type they're testing. For example, ThrowableSubject passes the description "throwable." Normally, Truth is able to infer this name from the class name. However, if we lack runtime type information (notably, under j2cl with class metadata off), we might not have access to the original class name.

      We don't expect to make this a public API: Class names are nearly always available. It's just that we want to be able to run Truth's own tests run with class metadata off, and it's easier to tweak the subjects to know their own names rather than generalize the tests to accept obfuscated names.

  • Method Details

    • isNull

      public void isNull()
      Fails if the subject is not null.

    • isNotNull

      public void isNotNull()
      Fails if the subject is null.

    • isEqualTo

      public void isEqualTo(Object expected)
      Fails if the subject is not equal to the given object. For the purposes of this comparison, two objects are equal if any of the following is true:
      • they are equal according to Objects.equal(java.lang.Object, java.lang.Object)
      • they are arrays and are considered equal by the appropriate Arrays.equals(long[], long[]) overload
      • they are boxed integer types (Byte, Short, Character, Integer, or Long) and they are numerically equal when converted to Long.
      • the actual value is a boxed floating-point type (Double or Float), the expected value is an Integer, and the two are numerically equal when converted to Double. (This allows assertThat(someDouble).isEqualTo(0) to pass.)

      Note: This method does not test the Object.equals(java.lang.Object) implementation itself; it assumes that method is functioning correctly according to its contract. Testing an equals implementation requires a utility such as guava-testlib's EqualsTester.

      In some cases, this method might not even call equals. It may instead perform other tests that will return the same result as long as equals is implemented according to the contract for its type.

    • standardIsEqualTo

      private void standardIsEqualTo(Object expected)

    • isNotEqualTo

      public void isNotEqualTo(Object unexpected)
      Fails if the subject is equal to the given object. The meaning of equality is the same as for the isEqualTo(java.lang.Object) method.

    • standardIsNotEqualTo

      private void standardIsNotEqualTo(Object unexpected)

    • compareForEquality

      private Subject.ComparisonResult compareForEquality(Object expected)
      Returns whether actual equals expected differ and, in some cases, a description of how they differ.

      The equality check follows the rules described on isEqualTo(java.lang.Object).

    • isIntegralBoxedPrimitive

      private static boolean isIntegralBoxedPrimitive(Object o)

    • integralValue

      private static long integralValue(Object o)

    • isSameInstanceAs

      public final void isSameInstanceAs(Object expected)
      Fails if the subject is not the same instance as the given object.

    • isNotSameInstanceAs

      public final void isNotSameInstanceAs(Object unexpected)
      Fails if the subject is the same instance as the given object.

    • isInstanceOf

      public void isInstanceOf(Class<?> clazz)
      Fails if the subject is not an instance of the given class.

    • isNotInstanceOf

      public void isNotInstanceOf(Class<?> clazz)
      Fails if the subject is an instance of the given class.

    • isIn

      public void isIn(Iterable<?> iterable)
      Fails unless the subject is equal to any element in the given iterable.

    • isAnyOf

      public void isAnyOf(Object first, Object second, Object... rest)
      Fails unless the subject is equal to any of the given elements.

    • isNotIn

      public void isNotIn(Iterable<?> iterable)
      Fails if the subject is equal to any element in the given iterable.

    • isNoneOf

      public void isNoneOf(Object first, Object second, Object... rest)
      Fails if the subject is equal to any of the given elements.

    • actual

      final Object actual()
      Returns the actual value under test.

    • actualCustomStringRepresentation

      protected String actualCustomStringRepresentation()
      Supplies the direct string representation of the actual value to other methods which may prefix or otherwise position it in an error message. This should only be overridden to provide an improved string representation of the value under test, as it would appear in any given error message, and should not be used for additional prefixing.

      Subjects should override this with care.

      By default, this returns String.ValueOf(getActualValue()).

    • actualCustomStringRepresentationForPackageMembersToCall

      final String actualCustomStringRepresentationForPackageMembersToCall()

    • formatActualOrExpected

      private String formatActualOrExpected(Object o)

    • base16

      private static String base16(byte[] bytes)

    • stringableIterable

      private static Iterable<?> stringableIterable(Object[] array)

    • checkByteArrayEquals

      private static Subject.ComparisonResult checkByteArrayEquals(byte[] expected, byte[] actual)
      Returns null if the arrays are equal. If not equal, returns a string comparing the two arrays, displaying them in the style "[1, 2, 3]" to supplement the main failure message, which uses the style "010203."

    • checkArrayEqualsRecursive

      private static Subject.ComparisonResult checkArrayEqualsRecursive(Object expectedArray, Object actualArray, String lastIndex)
      Returns null if the arrays are equal, recursively. If not equal, returns the string of the index at which they're different.

    • arrayType

      private static String arrayType(Object array)

    • gwtSafeObjectEquals

      private static boolean gwtSafeObjectEquals(Object actual, Object expected)

    • doubleArrayAsString

      private static List<String> doubleArrayAsString(double[] items)

    • floatArrayAsString

      private static List<String> floatArrayAsString(float[] items)

    • check

      @Deprecated final StandardSubjectBuilder check()
      Deprecated.
      Use the other overload, which requires you to supply more information to include in any failure messages.
      Returns a builder for creating a derived subject but without providing information about how the derived subject will relate to the current subject. In most cases, you should provide such information by using the other overload.

    • check

      protected final StandardSubjectBuilder check(String format, Object... args)
      Returns a builder for creating a derived subject.

      Derived subjects retain the FailureStrategy and messages of the current subject, and in some cases, they automatically supplement their failure message with information about the original subject.

      For example, ThrowableSubject.hasMessageThat(), which returns a StringSubject, is implemented with check("getMessage()").that(actual.getMessage()).

      The arguments to check describe how the new subject was derived from the old, formatted like a chained method call. This allows Truth to include that information in its failure messages. For example, assertThat(caught).hasCauseThat().hasMessageThat() will produce a failure message that includes the string "throwable.getCause().getMessage()," thanks to internal check calls that supplied "getCause()" and "getMessage()" as arguments.

      If the method you're delegating to accepts parameters, you can pass check a format string. For example, MultimapSubject.valuesForKey(java.lang.Object) calls check("valuesForKey(%s)", key).

      If you aren't really delegating to an instance method on the actual value -- maybe you're calling a static method, or you're calling a chain of several methods -- you can supply whatever string will be most useful to users. For example, if you're delegating to getOnlyElement(actual.colors()), you might call check("onlyColor()").

      Parameters:
      format - a template with %s placeholders
      args - the arguments to be inserted into those placeholders

    • checkNoNeedToDisplayBothValues

      final StandardSubjectBuilder checkNoNeedToDisplayBothValues(String format, Object... args)

    • doCheck

      private StandardSubjectBuilder doCheck(FailureMetadata.OldAndNewValuesAreSimilar valuesAreSimilar, String format, Object[] args)

    • ignoreCheck

      protected final StandardSubjectBuilder ignoreCheck()
      Begins a new call chain that ignores any failures. This is useful for subjects that normally delegate with to other subjects by using check() but have already reported a failure. In such cases it may still be necessary to return a Subject instance even though any subsequent assertions are meaningless. For example, if a user chains together more ThrowableSubject.hasCauseThat() calls than the actual exception has causes, hasCauseThat returns ignoreCheck().that(... a dummy exception ...).

    • failWithActual

      protected final void failWithActual(String key, Object value)
      Fails, reporting a message with two "facts":
      • key: value
      • but was: actual value.

      This is the simplest failure API. For more advanced needs, see the other overload and failWithoutActual.

      Example usage: The check contains(String) calls failWithActual("expected to contain", string).

    • failWithActual

      protected final void failWithActual(Fact first, Fact... rest)
      Fails, reporting a message with the given facts, followed by an automatically added fact of the form:
      • but was: actual value.

      If you have only one fact to report (and it's a key-value fact), prefer the simpler overload.

      Example usage: The check isEmpty() calls failWithActual(simpleFact("expected to be empty")).

    • failWithActual

      final void failWithActual(Iterable<Fact> facts)

    • failWithActual

      final void failWithActual(Facts facts)

    • fail

      @Deprecated final void fail(String check)
      Deprecated.
      Prefer to construct Fact-style methods, typically by using failWithActual(simpleFact(...)). However, if you want to preserve your exact failure message as a migration aid, you can inline this method (and then inline the resulting method call, as well).
      Reports a failure constructing a message from a simple verb.
      Parameters:
      check - the check being asserted

    • fail

      @Deprecated final void fail(String verb, Object other)
      Deprecated.
      Prefer to construct Fact-style methods, typically by using failWithActual(String, Object). However, if you want to preserve your exact failure message as a migration aid, you can inline this method (and then inline the resulting method call, as well).
      Assembles a failure message and passes such to the FailureStrategy
      Parameters:
      verb - the check being asserted
      other - the value against which the subject is compared

    • fail

      @Deprecated final void fail(String verb, Object... messageParts)
      Deprecated.
      Prefer to construct Fact-style methods, typically by using failWithActual(Fact, Fact...). However, if you want to preserve your exact failure message as a migration aid, you can inline this method.
      Assembles a failure message and passes such to the FailureStrategy
      Parameters:
      verb - the check being asserted
      messageParts - the expectations against which the subject is compared

    • failEqualityCheckForEqualsWithoutDescription

      final void failEqualityCheckForEqualsWithoutDescription(Object expected)
      Special version of failEqualityCheck(com.google.common.truth.Subject.EqualityCheck, java.lang.Object, com.google.common.truth.Subject.ComparisonResult) for use from IterableSubject, documented further there.

    • failEqualityCheck

      private void failEqualityCheck(Subject.EqualityCheck equalityCheck, Object expected, Subject.ComparisonResult difference)

    • tryFailForTrailingWhitespaceOnly

      private boolean tryFailForTrailingWhitespaceOnly(Object expected)
      Checks whether the actual and expected values are strings that match except for trailing whitespace. If so, reports a failure and returns true.

    • escapeWhitespace

      private static String escapeWhitespace(String in)

    • escapeWhitespace

      private static String escapeWhitespace(char c)

    • tryFailForEmptyString

      private boolean tryFailForEmptyString(Object expected)
      Checks whether the actual and expected values are empty strings. If so, reports a failure and returns true.

    • asUnicodeHexEscape

      private static char[] asUnicodeHexEscape(char c)

    • failEqualityCheckNoComparisonFailure

      private void failEqualityCheckNoComparisonFailure(Subject.ComparisonResult difference, Fact... facts)

    • failWithBadResults

      @Deprecated final void failWithBadResults(String verb, Object expected, String failVerb, Object actual)
      Deprecated.
      Prefer to construct Fact-style methods, typically by using failWithActual(Fact, Fact...). However, if you want to preserve your exact failure message as a migration aid, you can inline this method.
      Assembles a failure message and passes it to the FailureStrategy
      Parameters:
      verb - the check being asserted
      expected - the expectations against which the subject is compared
      failVerb - the failure of the check being asserted
      actual - the actual value the subject was compared against

    • failWithCustomSubject

      @Deprecated final void failWithCustomSubject(String verb, Object expected, Object actual)
      Deprecated.
      Prefer to construct Fact-style methods, typically by using failWithoutActual(Fact, Fact...). However, if you want to preserve your exact failure message as a migration aid, you can inline this method.
      Assembles a failure message with an alternative representation of the wrapped subject and passes it to the FailureStrategy
      Parameters:
      verb - the check being asserted
      expected - the expected value of the check
      actual - the custom representation of the subject to be reported in the failure.

    • failWithoutSubject

      @Deprecated final void failWithoutSubject(String check)
      Deprecated.
      Prefer to construct Fact-style methods, typically by using failWithoutActual(simpleFact(...)). However, if you want to preserve your exact failure message as a migration aid, you can inline this method.

    • failWithoutActual

      protected final void failWithoutActual(Fact first, Fact... rest)
      Fails, reporting a message with the given facts, without automatically adding the actual value.

      Most failure messages should report the actual value, so most checks should call failWithActual instead. However, failWithoutActual is useful in some cases:

      • when the actual value is obvious from the rest of the message. For example, isNotEmpty() calls failWithoutActual(simpleFact("expected not to be empty").
      • when the actual value shouldn't come last or should have a different key than the default of "but was." For example, isNotWithin(...).of(...) calls failWithoutActual so that it can put the expected and actual values together, followed by the tolerance.

      Example usage: The check isEmpty() calls failWithActual(simpleFact("expected to be empty")).

    • failWithoutActual

      final void failWithoutActual(Iterable<Fact> facts)

    • failWithoutActual

      final void failWithoutActual(Facts facts)

    • failWithoutActual

      @Deprecated final void failWithoutActual(String check)
      Deprecated.
      Prefer to construct Fact-style methods, typically by using failWithoutActual(simpleFact(...)). However, if you want to preserve your exact failure message as a migration aid, you can inline this method (and then inline the resulting method call, as well).
      Assembles a failure message without a given subject and passes it to the FailureStrategy
      Parameters:
      check - the check being asserted

    • equals

      @Deprecated public final boolean equals(Object o)
      Deprecated.
      Object.equals(Object) is not supported on Truth subjects. If you meant to test object equality between an expected and the actual value, use isEqualTo(Object) instead.
      Overrides:
      equals in class Object
      Throws:
      UnsupportedOperationException - always

    • hashCode

      @Deprecated public final int hashCode()
      Deprecated.
      Object.hashCode() is not supported on Truth subjects.
      Overrides:
      hashCode in class Object
      Throws:
      UnsupportedOperationException - always

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • butWas

      final Fact butWas()
      Returns a "but was: " string. This method should be rarely needed, since Truth inserts a "but was" fact by default for assertions. However, it's occasionally useful for calls to failWithoutActual that want a "but was" fact but don't want it to come last, where Truth inserts it by default.

    • typeDescription

      final String typeDescription()

    • typeDescriptionOrGuess

      private static String typeDescriptionOrGuess(Class<? extends Subject> clazz, String typeDescriptionOverride)

    • classMetadataUnsupported

      private static boolean classMetadataUnsupported()

    • doFail

      private void doFail(com.google.common.collect.ImmutableList<Fact> facts)

    • prependNameIfAny

      private com.google.common.collect.ImmutableList<Fact> prependNameIfAny(com.google.common.collect.ImmutableList<Fact> facts)

    • nameAsFacts

      private com.google.common.collect.ImmutableList<Fact> nameAsFacts()