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Tomer Figenblat
Tomer Figenblat

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Property-Based Matrix Testing in Java

#java #test #pbt #junit

I've used a common approach for property-based matrix testing in Java. Using JUnit's ParameterizedTest and a MethodSource annotations to point to a method as an argument supplier that spits out a stream representing a matrix.

It's pretty straightforward, but the more parameter types we have in our matrix, the harder it is to read or write the method supplying them. 😵

Let's take a look.
First, these are the two types for our matrix, these should spit out 6 test cases:

 enum Direction { INCOMING, OUTGOING } enum Status { SUCCESS, FAILURE, WAITING }
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Implementing a matrix from these Enums with JUnit's ParameterizedTest and a MethodSource:

 @ParameterizedTest @MethodSource("getArguments") void using_junit_parameterized_test_with_method_source( final Direction direction, final Status status) { assertTrue(true); } static Stream<Arguments> getArguments() { return Stream.of(Direction.values()) .flatMap(d -> Stream.of(Status.values()).map(s -> arguments(d, s))); }
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Adding members to the existing Enums will dynamically increase the matrix and, therefore, the number of tests performed; there's no need to modify the test code.

But, adding a third type to the matrix and the getArguments method will start losing its readability.

Lately, I discovered JUnit Pioneer, which is a JUnit 5 Extension Pack. Using its CartesianProductTest and CartesianEnumSource annotations, we can implement the same matrix simply and elegantly: 😃

 @CartesianProductTest @CartesianEnumSource(Direction.class) @CartesianEnumSource(Status.class) void using_junit_pioneer_cartesian_product_test_with_enum_source( final Direction direction, final Status status) { assertTrue(true); }
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This will spit out the same matrix, only now, adding a third element is quite simple: add another CartesianEnumSource annotation.

You can find other types of sources beside Enums, in JUnit Pioneer's Documentation.

As demonstrated in this repository, executing both matrix tests will print out:

[INFO] '-- JUnit Jupiter [OK] [INFO] '-- Property Based Matrix Test [OK] [INFO] +-- using junit pioneer cartesian product test with enum source (Direction, Status) [OK] [INFO] | +-- [1] INCOMING, SUCCESS [OK] [INFO] | +-- [2] INCOMING, FAILURE [OK] [INFO] | +-- [3] INCOMING, WAITING [OK] [INFO] | +-- [4] OUTGOING, SUCCESS [OK] [INFO] | +-- [5] OUTGOING, FAILURE [OK] [INFO] | '-- [6] OUTGOING, WAITING [OK] [INFO] '-- using junit parameterized test with method source (Direction, Status) [OK] [INFO] +-- [1] INCOMING, SUCCESS [OK] [INFO] +-- [2] INCOMING, FAILURE [OK] [INFO] +-- [3] INCOMING, WAITING [OK] [INFO] +-- [4] OUTGOING, SUCCESS [OK] [INFO] +-- [5] OUTGOING, FAILURE [OK] [INFO] '-- [6] OUTGOING, WAITING [OK]
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Check out the code for this tutorial in Github.

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