JUnit 5 Theories

[nrllewellyn]

Overview

Adds theories, in a form similar to JUnit 4's Theories. This will close ticket #395.

Substantial changes from JUnit 4:

• Methods allowed as sources of data points
• Streams and Iterators as accepted data point types, but only when produced by methods (since both are stateful, they have to come from a method so they can be read more than once)
• Suppliers system for simple data points (similar in form to parameterized tests, but allows mixing of in-line data points with class-level data points)
  • Specified via the ArgumentsSuppliedBy meta-annotation. This ties the annotation to a supplier class
  • Supplier class implements TheoryArgumentSupplier (or extends AbstractTheoryArgumentSupplier for common use cases). This class reads the annotation and produces the corresponding data points
  • Examples:

@Theory
public void myTheory(@IntValues(0, 42, 99) int someIntValue)

@Theory
public void myTheory(@ByteValues(0, 42) byte somByteValue, SomeClass valueFromClassLevelDataPoint)

• Qualifiers directly on theory parameters. Example:

@DataPoints(qualifiers = "nonZero")
private static final List<Double> GREATER_THAN_ZERO = Arrays.asList(3, 5, 7);

@DataPoint
private static final Double ZERO = 0;

@DataPoint(qualifiers = "nonZero")
private static final double NEGATIVE_NUMBER =  -4;

@Theory
public void testDivisionOperator(double dividend, @Qualifiers("nonZero") double divisor)

A few (very rough) examples can be found in:
junit-jupiter-theories/src/test/java/org/junit/jupiter/theories/TheoriesTestCase.java

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes
• All continuous integration builds pass

[nrllewellyn]

PR change list seems to have been corrupted during a rebase (probably user error on my part). Closing and re-opening PR to fix.