测试接口和默认方法
JUnit Jupiter允许在接口default
方法中声明@Test
,@RepeatedTest
,@ParameterizedTest
,@ TestFactory
,@TestTemplate
,@BeforeEach
和@AfterEach
。如果测试接口或测试类用@TestInstance(Lifecycle.PER_CLASS)
注解(请参阅测试实例生命周期),则可以在测试接口中的static
方法或接口default
方法上声明@BeforeAll
和@AfterAll
。这里有些例子。
@TestInstance(Lifecycle.PER_CLASS)
interface TestLifecycleLogger {
static final Logger LOG = Logger.getLogger(TestLifecycleLogger.class.getName());
@BeforeAll
default void beforeAllTests() {
LOG.info("Before all tests");
}
@AfterAll
default void afterAllTests() {
LOG.info("After all tests");
}
@BeforeEach
default void beforeEachTest(TestInfo testInfo) {
LOG.info(() -> String.format("About to execute [%s]",
testInfo.getDisplayName()));
}
@AfterEach
default void afterEachTest(TestInfo testInfo) {
LOG.info(() -> String.format("Finished executing [%s]",
testInfo.getDisplayName()));
}
}
interface TestInterfaceDynamicTestsDemo {
@TestFactory
default Collection<DynamicTest> dynamicTestsFromCollection() {
return Arrays.asList(
dynamicTest("1st dynamic test in test interface", () -> assertTrue(true)),
dynamicTest("2nd dynamic test in test interface", () -> assertEquals(4, 2 * 2))
);
}
}
可以在测试接口上声明@ExtendWith
和@Tag
,以便实现该接口的类自动继承其注解和扩展。请参阅测试执行前后的回调来获取TimingExtension的源代码。
@Tag("timed")
@ExtendWith(TimingExtension.class)
interface TimeExecutionLogger {
}
在你的测试类中,你可以实现这些测试接口来应用它们。
class TestInterfaceDemo implements TestLifecycleLogger,
TimeExecutionLogger, TestInterfaceDynamicTestsDemo {
@Test
void isEqualValue() {
assertEquals(1, 1, "is always equal");
}
}
运行TestInterfaceDemo
,输出类似以下内容:
:junitPlatformTest
INFO example.TestLifecycleLogger - Before all tests
INFO example.TestLifecycleLogger - About to execute [dynamicTestsFromCollection()]
INFO example.TimingExtension - Method [dynamicTestsFromCollection] took 13 ms.
INFO example.TestLifecycleLogger - Finished executing [dynamicTestsFromCollection()]
INFO example.TestLifecycleLogger - About to execute [isEqualValue()]
INFO example.TimingExtension - Method [isEqualValue] took 1 ms.
INFO example.TestLifecycleLogger - Finished executing [isEqualValue()]
INFO example.TestLifecycleLogger - After all tests
Test run finished after 190 ms
[ 3 containers found ]
[ 0 containers skipped ]
[ 3 containers started ]
[ 0 containers aborted ]
[ 3 containers successful ]
[ 0 containers failed ]
[ 3 tests found ]
[ 0 tests skipped ]
[ 3 tests started ]
[ 0 tests aborted ]
[ 3 tests successful ]
[ 0 tests failed ]
BUILD SUCCESSFUL
这个特性的另一个可以应用的地方是为接口契约编写测试。例如,您可以编写测试,验证Object.equals
或Comparable.compareTo
的实现应该如何如下表现。
public interface Testable<T> {
T createValue();
}
public interface EqualsContract<T> extends Testable<T> {
T createNotEqualValue();
@Test
default void valueEqualsItself() {
T value = createValue();
assertEquals(value, value);
}
@Test
default void valueDoesNotEqualNull() {
T value = createValue();
assertFalse(value.equals(null));
}
@Test
default void valueDoesNotEqualDifferentValue() {
T value = createValue();
T differentValue = createNotEqualValue();
assertNotEquals(value, differentValue);
assertNotEquals(differentValue, value);
}
}
public interface ComparableContract<T extends Comparable<T>> extends Testable<T> {
T createSmallerValue();
@Test
default void returnsZeroWhenComparedToItself() {
T value = createValue();
assertEquals(0, value.compareTo(value));
}
@Test
default void returnsPositiveNumberComparedToSmallerValue() {
T value = createValue();
T smallerValue = createSmallerValue();
assertTrue(value.compareTo(smallerValue) > 0);
}
@Test
default void returnsNegativeNumberComparedToSmallerValue() {
T value = createValue();
T smallerValue = createSmallerValue();
assertTrue(smallerValue.compareTo(value) < 0);
}
}
在你的测试类中,你可以实现两个契约接口,从而继承相应的测试。当然你必须实现抽象方法。
class StringTests implements ComparableContract<String>, EqualsContract<String> {
@Override
public String createValue() {
return "foo";
}
@Override
public String createSmallerValue() {
return "bar"; // 'b' < 'f' in "foo"
}
@Override
public String createNotEqualValue() {
return "baz";
}
}
上述测试仅仅是作为例子,因此不完整。
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