cajon-plugin/README.md

# Cajon - Concise AssertJ Optimizing Nitpicker

Cajon is an IntelliJ IDEA Plugin for shortening and optimizing [AssertJ](https://assertj.github.io/doc/) assertions.

## Purpose

First, code is easier to read, when it is concise and reflects the intention clearly.
AssertJ has plenty of different convenience methods that describing various intentions precisely.
Why write longer, more complex code that can be expressed in brevity?

Second, when using the available special assertion methods of AssertJ, a failure of a condition
can be expressed in better detail and with more meaningful descriptions.
This makes finding bugs and fixing failed tests more efficient.
Nobody likes to read failures of the kind "failed because true is not false".

For example:

```
assertThat(collection.size()).isEqualTo(5);
```

If the collection has more or less than five elements, the assertion will fail, but will not
tell you about the contents, making it hard to guess what went wrong.

Instead, if you wrote the same assertion the following way:

```
assertThat(collection).hasSize(5);
```

Then AssertJ would tell you the _actual contents_ of the collection on failure.

## Conversion of JUnit assertions to AssertJ

The plugin also supports the conversion of the most common JUnit 4 assertions to AssertJ.

## Lookup and refactoring of string-based extracting()

AssertJ allows [extracting POJO fields/properties on iterables/arrays](http://joel-costigliola.github.io/assertj/assertj-core-features-highlight.html#extracted-properties-assertion).

Using strings is not safe for refactoring (and before Java 8 Lambdas were available,
creating extractor functions just for testing purpose was a bit too tedious).

This plugin adds support for referencing these fields (so you can ctrl(/cmd)-click on the 
string to go to the definition) and also allows safe refactoring on the 
fields (refactoring a getter method without a corresponding field will not work 
correctly right now).

## Usage

The plugin will report inspections in your opened editor file as warnings.
You can then quick-fix these with your quick-fix hotkey (usually Alt-Return or Opt-Return).

Or, you can use the "Run Inspection by Name..." action to run one inspection on a bigger scope (e.g. the whole project).
Applying a quick fix might result in further optimization possibilities, so 
you might need to perform a couple of fixes before you get to the final result.

Check out this example where every line represents the result after a Cajon quickfix:
```
assertFalse(!(array.length == collection.size()));

assertThat(!(array.length == collection.size())).isFalse();

assertThat(array.length == collection.size()).isTrue();

assertThat(array.length).isEqualTo(collection.size());

assertThat(array).hasSameSizeAs(collection);
```

You can toggle the various inspections in the Settings/Editor/Inspections in the AssertJ group.

## Implemented inspections and quickfixes

- JoinAssertThatStatements
  ```
  from: assertThat(expected).someCondition();
        assertThat(expected).anotherCondition();
    to: assertThat(expected).someCondition().anotherCondition();
  ```
  Joining will work on actual expressions inside assertThat() that are equivalent expressions,
  except for method calls with known side-effect methods such as ```Iterator.next()``` -- please notify me about others.

  The comments of the statements will be preserved. When using ```.extracting()``` or similar, the statements will not be merged.
    
- AssertThatObjectIsNullOrNotNull
  ```
  from: assertThat(object).isEqualTo(null);
    to: assertThat(object).isNull();

  from: assertThat(object).isNotEqualTo(null);  
    to: assertThat(object).isNotNull();
  ```

- AssertThatBooleanCondition
  ```
  from: assertThat(booleanValue).isEqualTo(true/false/Boolean.TRUE/Boolean.FALSE);  
    to: assertThat(booleanValue).isTrue()/isFalse();
  ```

- AssertThatInvertedBooleanCondition
  ```
  from: assertThat(!booleanValue).isEqualTo(true/false/Boolean.TRUE/Boolean.FALSE);  
  from: assertThat(!booleanValue).isTrue()/isFalse();  
    to: assertThat(booleanValue).isFalse()/isTrue();
  ```

- AssertThatInstanceOf
  ```
  from: assertThat(object instanceof classname).isEqualTo(true);
  from: assertThat(object instanceof classname).isTrue();
    to: assertThat(object).isInstanceOf(classname.class);

  from: assertThat(object instanceof classname).isEqualTo(false);
  from: assertThat(object instanceof classname).isFalse();
    to: assertThat(object).isNotInstanceOf(classname.class);
  ```

- AssertThatStringIsEmpty
  ```
  from: assertThat(charSequence/string).isEqualTo("");
  from: assertThat(charSequence/string).hasSize(0);
    to: assertThat(charSequence/string).isEmpty();
  ```

- AssertThatStringExpression
  ```
  from: assertThat(stringActual.isEmpty()).isTrue();
    to: assertThat(stringActual).isEmpty();

  from: assertThat(stringActual.equals(stringExpected)).isTrue();
  from: assertThat(stringActual.contentEquals(charSeqExpected)).isTrue();
    to: assertThat(stringActual).isEqualTo(stringExpected);

  from: assertThat(stringActual.equalsIgnoreCase(stringExpected)).isTrue();
    to: assertThat(stringActual).isEqualToIgnoringCase(stringExpected);

  from: assertThat(stringActual.contains(stringExpected)).isTrue();
    to: assertThat(stringActual).contains(stringExpected);

  from: assertThat(stringActual.startsWith(stringExpected)).isTrue();
    to: assertThat(stringActual).startsWith(stringExpected);

  from: assertThat(stringActual.endsWith(stringExpected)).isTrue();
    to: assertThat(stringActual).endsWith(stringExpected);
  ```
  Analogously with ```isFalse()```.

- AssertThatEnumerableIsEmpty
  ```
  from: assertThat(enumerable).hasSize(0);
    to: assertThat(enumerable).isEmpty();
  ```

- AssertThatSize
  ```
  from: assertThat(array.length).isEqualTo(0);
  from: assertThat(array.length).isLessThanOrEqualTo(0);
  from: assertThat(array.length).isLessThan(1);
  from: assertThat(array.length).isZero();
    to: assertThat(array).isEmpty();

  from: assertThat(array.length).isGreaterThan(0);
  from: assertThat(array.length).isGreaterThanOrEqualTo(1);
  from: assertThat(array.length).isNotZero();
    to: assertThat(array).isNotEmpty();

  from: assertThat(array.length).isEqualTo(anotherArray.length);
    to: assertThat(array).hasSameSizeAs(anotherArray);
    
  from: assertThat(array).hasSize(anotherArray.length);
    to: assertThat(array).hasSameSizeAs(anotherArray);
  ```

  and additionally with AssertJ 13.2.0 or later

  ```
  from: assertThat(array.length).isLessThanOrEqualTo(expression);
    to: assertThat(array).hasSizeLessThanOrEqualTo(expression);
    
  from: assertThat(array.length).isLessThan(expression);
    to: assertThat(array).hasSizeLessThan(expression);

  from: assertThat(array.length).isGreaterThan(expression);
    to: assertThat(array).hasSizeGreaterThan(expression);

  from: assertThat(array.length).isGreaterThanOrEqualTo(expression);
    to: assertThat(array).hasSizeGreaterThanOrEqualTo(expression);
  ```
  and analogously for collections, strings and CharSequences, e.g:

  ```
  from: assertThat("string".length()).isLessThan(1);
    to: assertThat("string").isEmpty();

  from: assertThat("string".length()).isEqualTo(collection.size())
    to: assertThat("string").hasSameSizeAs(collection);
    
  from: assertThat("string".length()).hasSize("strong".length())
    to: assertThat("string").hasSameSizeAs("strong");
  ```

- AssertThatBinaryExpression
  ```
  from: assertThat(primActual == primExpected).isTrue();
    to: assertThat(primActual).isEqualTo(primExpected);

  from: assertThat(10 < primActual).isNotEqualTo(false);
    to: assertThat(primActual).isGreaterThan(primExpected);

  from: assertThat(objActual != objExpected).isEqualTo(true);
    to: assertThat(objActual).isNotSameAs(objExpected);

  from: assertThat(null == objActual).isFalse();
    to: assertThat(objActual).isNotNull();

  from: assertThat(objActual.equals(objExpected).isTrue();
    to: assertThat(objActual).isEqualTo(objExpected);
  ```
  ...and many, many more combinations (more than 150).

- AssertThatJava8Optional
  ```
  from: assertThat(opt.isPresent()).isEqualTo(true);
  from: assertThat(opt.isPresent()).isNotEqualTo(false);
  from: assertThat(opt.isPresent()).isTrue();
    to: assertThat(opt).isPresent();

  from: assertThat(opt.isPresent()).isEqualTo(false);
  from: assertThat(opt.isPresent()).isNotEqualTo(true);
  from: assertThat(opt.isPresent()).isFalse();
    to: assertThat(opt).isNotPresent();
    
  from: assertThat(opt.get()).isEqualTo("foo");
    to: assertThat(opt).contains("foo");
     
  from: assertThat(opt.get()).isSameAs("foo");
    to: assertThat(opt).containsSame("foo"); 

  from: assertThat(opt).isEqualTo(Optional.of("foo"));
  from: assertThat(opt).isEqualTo(Optional.ofNullable("foo"));
    to: assertThat(opt).contains("foo"); 

  from: assertThat(opt).isEqualTo(Optional.empty());
    to: assertThat(opt).isNotPresent();

  from: assertThat(opt).isNotEqualTo(Optional.empty());
    to: assertThat(opt).isPresent();
  ```

- AssertThatGuavaOptional
  ```
  from: assertThat(opt.isPresent()).isEqualTo(true);
  from: assertThat(opt.isPresent()).isNotEqualTo(false);
  from: assertThat(opt.isPresent()).isTrue();
    to: assertThat(opt).isPresent();

  from: assertThat(opt.isPresent()).isEqualTo(false);
  from: assertThat(opt.isPresent()).isNotEqualTo(true);
  from: assertThat(opt.isPresent()).isFalse();
    to: assertThat(opt).isAbsent();
    
  from: assertThat(opt.get()).isEqualTo("foo");
    to: assertThat(opt).contains("foo");
     
  from: assertThat(opt).isEqualTo(Optional.of("foo"));
  from: assertThat(opt).isEqualTo(Optional.fromNullable("foo"));
    to: assertThat(opt).contains("foo"); 

  from: assertThat(opt).isEqualTo(Optional.absent());
    to: assertThat(opt).isAbsent();

  from: assertThat(opt).isNotEqualTo(Optional.absent());
    to: assertThat(opt).isPresent();
  ```

  AssertJ for Guava needs to be available in the classpath.

- JUnitAssertToAssertJ
  ```
  assertTrue(condition);
  assertTrue(message, condition);
  assertFalse(condition);
  assertFalse(message, condition);
  assertNull(object);
  assertNull(message, object);
  assertNonNull(object);
  assertNonNull(message, object);
  assertEquals(expected, actual);
  assertEquals(message, expected, actual);
  assertEquals(expectedDoubleOrFloat, actualDoubleOrFloat, delta);
  assertEquals(message, expectedDoubleOrFloat, actualDoubleOrFloat, delta);
  assertNotEquals(unexpected, actual);
  assertNotEquals(message, unexpected, actual);
  assertNotEquals(unexpectedDoubleOrFloat, actualDoubleOrFloat, delta);
  assertNotEquals(message, unexpectedDoubleOrFloat, actualDoubleOrFloat, delta);
  assertSame(expected, actual);
  assertSame(message, expected, actual);
  assertNotSame(unexpected, actual);
  assertNotSame(message, unexpected, actual);
  assertArrayEquals(expected, actual);
  assertArrayEquals(message, expectedArray, actualArray);
  assertArrayEquals(expectedDoubleOrFloatArray, actualDoubleOrFloatArray, delta);
  assertArrayEquals(message, expectedDoubleOrFloatArray, actualDoubleOrFloatArray, delta);
  ```

### Implemented referencing

  ```
  .extracting("field")
  .extracting("outerField.fieldInsideObjectTypeOfOuterField.andSoOn")
  .extracting("property") // where the class has a getProperty() (or isProperty() for boolean) method
  .extracting("bareMethod") // supported with AssertJ 13.12.0
  .extracting(Extractors.byName("fieldOrPropertyOrBareMethod")
  .extracting(Extractors.byName("fieldOrPropertyOrBareMethod.orAPathLikeAbove")
  .extracting(Extractors.resultOf("bareMethod")
  .extractingResultOf("bareMethod")
  .flatExtracting("fieldOrPropertyOrBareMethod.orAPathLikeAbove")
  .flatExtracting(Extractors.byName("fieldOrPropertyOrBareMethod.orAPathLikeAbove")
  .flatExtracting(Extractors.resultOf("bareMethod")
  ```
  Works on both POJOs and ```Iterable```s/```Array```s. 
  Implementation is very basic though and does not work with fancy cascaded .extracting() sequences.
  If there's demand, I will add it.

## Development notice

Cajon is written in Kotlin 1.3.

Cajon is probably the only plugin that uses JUnit 5 Jupiter for unit testing so far (or at least the only one that I'm aware of ;) ).
The IntelliJ framework actually uses the JUnit 3 TestCase for plugin testing and it took me quite a while to make it work with JUnit 5.
Feel free to use the code (in package de.platon42.intellij.jupiter) for your projects (with attribution).

## Planned features
- AssumeThatInsteadOfReturn
- Extraction with property names to lambda with Java 8
  ```
  from: assertThat(object).extracting("propOne", "propNoGetter", "propTwo.innerProp")...
    to: assertThat(object).extracting(type::getPropOne, it -> it.propNoGetter, it -> it.getPropTwo().getInnerProp())...
  ```

- Kotlin support (right now, however, with less than 100 downloads after a month, this is unlikely to happen)

## Changelog

#### V0.8 (unreleased)
- Fixed missing description for JoinAssertThatStatements and detection of equivalent expressions (sorry, released it too hastily).
- Fixed ```isEmpty()``` for enumerables and strings and ```isNull()``` for object conversions to be applied only if it is the terminal method call as ```isEmpty()``` and ```isNull()``` return void.

#### V0.7 (28-Apr-19)
- Another fix for AssertThatGuavaOptional inspection regarding using the same family name for slightly different quick fix executions
  (really, Jetbrains, this sucks for no reason).
- Extended AssertThatSize inspection to transform ```hasSize()``` into ```hasSameSizeAs()```, if possible.
- Implemented first version of JoinAssertThatStatements inspection that will try to merge ```assertThat()``` statements with the same
  actual object together, preserving comments.

#### V0.6 (22-Apr-19)
- New AssertThatStringExpression inspection that will move ```isEmpty()```, ```equals()```, ```equalsIgnoreCase()```, ```contains()```,
  ```startsWith()```, and ```endsWith()``` out of actual expression.
- Extended AssertThatSize inspection to take ```String```s and ```CharSequences``` into account, too.
- New AssertThatInvertedBooleanCondition inspection that will remove inverted boolean expressions inside ```assertThat()```.
- Renamed a few inspections to better/shorter names.
- New AssertThatInstanceOf inspection that moves instanceof expressions out of ```assertThat()```.

#### V0.5 (18-Apr-19)
- Fixed incompatibility with IDEA versions < 2018.2 (affected AssertThatSizeInspection). Minimal version is now 2017.3.
- Fixed missing Guava imports (if not already present) for AssertThatGuavaInspection. This was a major PITA to get right.
- Added support for referencing and refactoring inside ```.extracting()``` methods with fields, properties and methods (though
  getter renaming does not work that perfect, but I'm giving up for now as the IntelliJ SDK docs are seriously lacking).
- Fixed an exception in batch mode if the description string was the same but for different fixes. 
  Now descriptions are different for quick fixes triggered by AssertThatJava8OptionalInspection and AssertThatGuavaOptionalInspection.

#### V0.4 (11-Apr-19)
- Reduced minimal supported IDEA version from 2018.2 to 2017.2.
- New inspection AssertThatJava8Optional that operates on Java 8 ```Optional``` objects and tries to use ```contains()```, ```containsSame()```, ```isPresent()```, and ```isNotPresent()``` instead.
- New inspection AssertThatGuavaOptional that operates on Guava ```Optional``` objects and tries to use ```contains()```, ```isPresent()```, and ```isAbsent()``` instead.
- Added support in AssertThatBinaryExpressionIsTrueOrFalse for ```is(Not)EqualTo(Boolean.TRUE/FALSE)```.

#### V0.3 (07-Apr-19)
- New inspection AssertThatBinaryExpressionIsTrueOrFalse that will find and fix common binary expressions and ```equals()``` statements (more than 150 combinations) inside ```assertThat()```.
- Merged AssertThatObjectIsNull and AssertThatObjectIsNotNull to AssertThatObjectIsNullOrNotNull.
- Support for ```hasSizeLessThan()```, ```hasSizeLessThanOrEqualTo()```, ```hasSizeGreaterThanOrEqualTo()```, and ```hasSizeGreaterThan()``` for AssertThatSizeInspection (with AssertJ >=13.2.0).
- Really fixed highlighting for JUnit conversion. Sorry.

#### V0.2 (01-Apr-19)
- Fixed descriptions and quick fix texts.
- Fixed highlighting of found problems and also 'Run inspection by Name' returning nothing.

#### V0.1 (31-Mar-19)
- Initial release.