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Tests

rascal-0.34.0

Synopsis​

A unit testing and regressing testing framework is builtin to the Rascal language

Description​

To write a test in Rascal, use the test modifier on a parametrized Function declaration:

test bool integerAdditionIsCommutative(int a, int b) {      ❶  
    return a + b == b + a;      ❷  
}

test bool integerMultiplicationIsCommutative(int a, int b)
    = a * b == b * a;      ❸
  • ❶ a function header defines test parameters for which a few hundred examples will be randomly generated. The name of the function services as the name of the test
    • You can call a test function like any other function
    • Test functions are not to be overloaded. Use unique names for unique tests.
  • ❷ the function returns true or false as the "test", but you can also not throw an exception for success and Throw one for failure.
  • ❸ all sorts of Function are allowed.
  • For complex parameter types like Algebraic Data Types also random inputs will be generated that satisfy the grammar.
  • For functions with multiple parameters, sometimes the random code generator will provide structurally equal parameters for successive arguments if the types allow this, or even values shared in memory.
  • Also the "random" input generator may specialize towards patterns that are found in the bodies of the functions-under-test, to achieve coverage faster. In other words, neither coverage nor uniform randomness is guaranteed. Expect something in between.

Running Tests​

This command will run all tested in the imported modules and also any locally defined tests:

rascal>:test

Then there is the RascalJUnitTestRunner and RascalJUnitParallelRecursiveTestRunner Java classes which you can use to annotate your own test class which will then load the given test modules:

package org.rascalmpl.test.basic;

import org.junit.runner.RunWith;
import org.rascalmpl.test.infrastructure.RascalJUnitTestPrefix;
import org.rascalmpl.test.infrastructure.RascalJUnitTestRunner;

@RunWith(RascalJUnitTestRunner.class)                     ❶  
@RascalJUnitTestPrefix("lang::rascal::tests::basic")      ❷  
public class RunRascalTestModules { }
  • ❶ selects the test runner (parallel or not)
  • ❷ selects the root package to search for modules and tests
  • Then use JUnit configuration in Eclipse, VScode or Maven to activate the tests at the right time.
  • Reporting goes through standard JUnit reporting, so this integrates well with IDEs and continuous integration systems like Jenkins and GitHub Actions.