Why is this an issue?

AssertJ contains many assertions methods specific to common types. Both versions will test the same things, but the dedicated one will provide a better error message, simplifying the debugging process.

This rule reports an issue when an assertion can be simplified to a dedicated one.

The array below gives a non-exhaustive list of assertion reported by the rule. Code behaving similarly, or with a negation will also be reported.

Original	Dedicated
Related to Object
`assertThat(getObject()).isEqualTo(null)`	`assertThat(getObject()).isNull()`
`assertThat(getBoolean()).isEqualTo(true)`	`assertThat(getBoolean()).isTrue()`
`assertThat(getBoolean()).isEqualTo(false)`	`assertThat(getBoolean()).isFalse()`
`assertThat(x.equals(y)).isTrue()`	`assertThat(x).isEqualTo(y)`
`assertThat(x == y).isTrue()`	`assertThat(x).isSameAs(y)`
`assertThat(x == null).isTrue()`	`assertThat(x).isNull()`
`assertThat(x.toString()).isEqualTo(y)`	`assertThat(x).hasToString(y)`
`assertThat(x.hashCode()).isEqualTo(y.hashCode())`	`assertThat(x).hasSameHashCodeAs(y)`
`assertThat(getObject() instanceof MyClass).isTrue()`	`assertThat(getObject()).isInstanceOf(MyClass.class)`
Related to `Comparable`
`assertThat(x.compareTo(y)).isZero()`	`assertThat(x).isEqualByComparingTo(y)`
`assertThat(x >= y).isTrue()`	`assertThat(x).isGreaterThanOrEqualTo(y)`
`assertThat(x > y).isTrue()`	`assertThat(x).isGreaterThan(y)`
`assertThat(x <= y).isTrue()`	`assertThat(x).isLessThanOrEqualTo(y)`
`assertThat(x < y).isTrue()`	`assertThat(x).isLessThan(y)`
Related to `String`
`assertThat(getString().isEmpty()).isTrue()`	`assertThat(getString()).isEmpty()`
`assertThat(getString()).hasSize(0)`	`assertThat(getString()).isEmpty()`
`assertThat(getString().equals(expected)).isTrue()`	`assertThat(getString()).isEqualTo(expected)`
`assertThat(getString().equalsIgnoreCase(expected)).isTrue()`	`assertThat(getString()).isEqualToIgnoringCase(expected)`
`assertThat(getString().contains(expected)).isTrue()`	`assertThat(getString()).contains(expected)`
`assertThat(getString().startsWith(expected)).isTrue()`	`assertThat(getString()).startsWith(expected)`
`assertThat(getString().endsWith(expected)).isTrue()`	`assertThat(getString()).endsWith(expected)`
`assertThat(getString().matches(expected)).isTrue()`	`assertThat(getString()).matches(expected)`
`assertThat(getString().trim()).isEmpty()`	`assertThat(getString()).isBlank()`
`assertThat(getString().length()).isEqualTo(length)`	`assertThat(getString()).hasSize(length)`
`assertThat(getString().length()).hasSize(expected.length())`	`assertThat(getString()).hasSameSizeAs(expected)`
Related to `File`
`assertThat(getFile()).hasSize(0)`	`assertThat(getFile()).isEmpty()`
`assertThat(getFile().length()).isZero()`	`assertThat(getFile()).isEmpty()`
`assertThat(getFile().length()).isEqualTo(length)`	`assertThat(getFile()).hasSize(length)`
`assertThat(getFile().canRead()).isTrue()`	`assertThat(getFile()).canRead()`
`assertThat(getFile().canWrite()).isTrue()`	`assertThat(getFile()).canWrite()`
`assertThat(getFile().exists()).isTrue()`	`assertThat(getFile()).exists()`
`assertThat(getFile().getName()).isEqualTo(name)`	`assertThat(getFile()).hasName(name)`
`assertThat(getFile().getParent()).isEqualTo(pathname)`	`assertThat(getFile()).hasParent(pathname)`
`assertThat(getFile().getParentFile()).isNull()`	`assertThat(getFile()).hasNoParent()`
`assertThat(getFile().isAbsolute()).isTrue()`	`assertThat(getFile()).isAbsolute()`
`assertThat(getFile().isAbsolute()).isFalse()`	`assertThat(getFile()).isRelative()`
`assertThat(getFile().isDirectory()).isTrue()`	`assertThat(getFile()).isDirectory()`
`assertThat(getFile().isFile()).isTrue()`	`assertThat(getFile()).isFile()`
`assertThat(getFile().list()).isEmpty()`	`assertThat(getFile()).isEmptyDirectory()`
Related to `Path`
`assertThat(getPath().startsWith(path)).isTrue()`	`assertThat(getPath()).startsWithRaw(path)`
`assertThat(getPath().endsWith(path)).isTrue()`	`assertThat(getPath()).endsWithRaw(path)`
`assertThat(getPath().getParent()).isEqualTo(name)`	`assertThat(getPath()).hasParentRaw(name)`
`assertThat(getPath().getParent()).isNull()`	`assertThat(getPath()).hasNoParentRaw()`
`assertThat(getPath().isAbsolute()).isTrue()`	`assertThat(getPath()).isAbsolute()`
`assertThat(getPath().isAbsolute()).isFalse()`	`assertThat(getPath()).isRelative()`
Related to `Array`
`assertThat(getArray().length).isZero()`	`assertThat(getArray()).isEmpty()`
`assertThat(getArray().length).isEqualTo(length)`	`assertThat(getArray()).hasSize(length)`
`assertThat(getArray().length).isEqualTo(anotherArray.length)`	`assertThat(getArray()).hasSameSizeAs(anotherArray)`
`assertThat(getArray().length).isLessThanOrEqualTo(expression)`	`assertThat(getArray()).hasSizeLessThanOrEqualTo(expression)`
`assertThat(getArray().length).isLessThan(expression)`	`assertThat(getArray()).hasSizeLessThan(expression)`
`assertThat(getArray().length).isGreaterThan(expression)`	`assertThat(getArray()).hasSizeGreaterThan(expression)`
`assertThat(getArray().length).isGreaterThanOrEqualTo(expression)`	`assertThat(getArray()).hasSizeGreaterThanOrEqualTo(expression)`
Related to `Collection`
`assertThat(getCollection().isEmpty()).isTrue()`	`assertThat(getCollection()).isEmpty()`
`assertThat(getCollection().size()).isZero()`	`assertThat(getCollection()).isEmpty()`
`assertThat(getCollection().contains(something)).isTrue()`	`assertThat(getCollection()).contains(something)`
`assertThat(getCollection().containsAll(otherCollection)).isTrue()`	`assertThat(getCollection()).containsAll(otherCollection)`
Related to `Map`
`assertThat(getMap().size()).isEqualTo(otherMap().size()`	`assertThat(getMap()).hasSameSizeAs(otherMap())`
`assertThat(getMap().containsKey(key)).isTrue()`	`assertThat(getMap()).containsKey(key)`
`assertThat(getMap().keySet()).contains(key)`	`assertThat(getMap()).containsKey(key)`
`assertThat(getMap().keySet()).containsOnlyKey(key)`	`assertThat(getMap()).containsOnlyKey(key)`
`assertThat(getMap().containsValue(value)).isTrue()`	`assertThat(getMap()).containsValue(value)`
`assertThat(getMap().values()).contains(value)`	`assertThat(getMap()).containsValue(value)`
`assertThat(getMap().get(key)).isEqualTo(value)`	`assertThat(getMap()).containsEntry(key, value)`
Related to `Optional`
`assertThat(getOptional().isPresent()).isTrue()`	`assertThat(getOptional()).isPresent()`
`assertThat(getOptional().get()).isEqualTo(something)`	`assertThat(getOptional()).contains(something)`
`assertThat(getOptional().get()).isSameAs(something)`	`assertThat(getOptional()).containsSame(something)`

Noncompliant code example

assertThat(getObject()).isEqualTo(null); // Noncompliant
assertThat(getObject()).isNotEqualTo(null); // Noncompliant - not listed above but also supported

assertThat(getString().trim()).isEmpty();
assertThat(getFile().canRead()).isTrue();
assertThat(getPath().getParent()).isNull();

Compliant solution

assertThat(getObject()).isNull();
assertThat(getObject()).isNotNull();

assertThat(getString()).isBlank();
assertThat(getFile()).canRead();
assertThat(getPath()).hasNoParentRaw();