Tester for hamcrest Matchers

Matcher, used for test or not, must also be tested. Powerunit provides a way to test Matcher in a simple way.

The class MatcherTester exposes a DSL to create build a tester, based on the concept of Test Framework. Let's assume you have a matcher on String that check for equality. It is possible to wrote a test in the following way :

import ch.powerunit.TestDelegate;
import ch.powerunit.TestSuite;
import ch.powerunit.matchers.MatcherTester;
import static ch.powerunit.matchers.MatcherTester.*;

public class MatcherTesterTest implements TestSuite {

  @TestDelegate
  public final MatcherTester<TestMatcher> tester = MatcherTester.of(TestMatcher.class).with(
      matcher(new TestMatcher(null)).describedAs("is null")
          .nullAccepted().rejecting(value("x").withMessage(" was \"x\"")),
      matcher(new TestMatcher("x")).describedAs("is \"x\"")
          .nullRejected(" was null").accepting("x").rejecting(value("y").withMessage(" was \"y\"")),
      matcher(new TestMatcher("y")).describedAs("is \"y\"")
          .nullRejected(" was null").accepting("y").rejecting(value("x").withMessage(" was \"x\"")));
}

The framework provides a way to declare several expectation (test fixtures) for a Matcher. It starts with a <MatcherTester.of(theclass).with(one or several validation). Each of these validation are builded by using the syntax matcher(instance of matcher).describedAs(expected message or matcher). followed by several of the following :

• nullAccepted()
• nullRejected()
• accepting(list of expected value)
• rejecting(...) Each rejecting clause is defined by value(rejected value).withMessage( expected message or matcher)

  Error of validation will be integrated in the normal test result, like for instance :

  Failed tests:
          Validate that a value (x) is accepted for the matcher of class class ch.powerunit.examples.MatcherTesterTest$TestMatcher (TestMatcher [target=x]) of ch.powerunit.examples.MatcherTesterTest caused by Validate x is accepted by this matcher
  expecting <true> but was <false>
          Validate that a value (y) is rejected for the matcher of class class ch.powerunit.examples.MatcherTesterTest$TestMatcher (TestMatcher [target=x] then " was \"y\"") of ch.powerunit.examples.MatcherTesterTest caused by Validate y is rejected by this matcher
  expecting <false> but was <true>
          Validate that a value (y) is accepted for the matcher of class class ch.powerunit.examples.MatcherTesterTest$TestMatcher (TestMatcher [target=y]) of ch.powerunit.examples.MatcherTesterTest caused by Validate y is accepted by this matcher
  expecting <true> but was <false>
          Validate that a value (x) is rejected for the matcher of class class ch.powerunit.examples.MatcherTesterTest$TestMatcher (TestMatcher [target=y] then " was \"x\"") of ch.powerunit.examples.MatcherTesterTest caused by Validate x is rejected by this matcher
  expecting <false> but was <true>