TODO [Assertions](https://junit.org/junit5/docs/5.0.1/api/org/junit/jupiter/api/Assertions.html)
TODO [快速看一眼JUnit 5](https://www.ithome.com.tw/voice/117883)
TODO [JUnit 5 User Guide](https://junit.org/junit5/docs/current/user-guide/)
```java
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.mockito.Mockito.when;
@ExtendWith(MockitoExtension.class)
public class CalculatorServiceTest {
@Mock
private CalculatorService calculatorService;
@InjectMocks
private CalculatorController calculatorController;
@Test
public void testAddition() {
// Arrange
int a = 5;
int b = 10;
int expectedResult = 15;
when(calculatorService.add(a, b)).thenReturn(expectedResult);
// Act
int result = calculatorController.add(a, b);
// Assert
assertThat(result, is(equalTo(expectedResult)));
}
}
```
```java
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.endsWith;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.greaterThan;
import static org.hamcrest.Matchers.greaterThanOrEqualTo;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.lessThan;
import static org.hamcrest.Matchers.lessThanOrEqualTo;
import static org.hamcrest.Matchers.not;
import static org.hamcrest.Matchers.notNullValue;
import static org.hamcrest.Matchers.nullValue;
import static org.hamcrest.Matchers.startsWith;
public class HamcrestExamples {
public static void main(String[] args) {
// equalTo / is
assertThat(10, Matchers.equalTo(10));
assertThat(10, Matchers.is(10));
// not
assertThat(10, Matchers.not(Matchers.equalTo(20)));
// nullValue / notNullValue
assertThat(null, Matchers.nullValue());
assertThat("Hello", Matchers.notNullValue());
// containsString
assertThat("Hello, World!", Matchers.containsString("World"));
// startsWith
assertThat("Hello, World!", Matchers.startsWith("Hello"));
// endsWith
assertThat("Hello, World!", Matchers.endsWith("!"));
// greaterThan
assertThat(15, Matchers.greaterThan(10));
// lessThan
assertThat(5, Matchers.lessThan(10));
// greaterThanOrEqualTo
assertThat(10, Matchers.greaterThanOrEqualTo(10));
// lessThanOrEqualTo
assertThat(5, Matchers.lessThanOrEqualTo(10));
}
}
```