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在软件工程领域，无论对于前端或是后端工程师都必须对自己的代码质量负责，尤其是后端工程师，高度的单元测试覆盖率是最有效的手段之一。
以Java代码为例，有着Junit、Mockito等开源单元测试框架，并且非常便于测试集成。Golang自身便带有单元测试模块，都是为提高软件质量而设计的，优秀的开源框架其单元测试覆盖率都非常高，才能为其软件质量提供保障。
一名优秀的后端工程师必须具备编写单元测试的习惯，而且测试覆盖率越高你的软件质量也就越好，其次高度覆盖的测试用例方便软件的迭代与维护，能够有助于后者快速理解代码与定位问题。
高覆盖体现在测试用例覆盖public方法、函数中的if-else等逻辑、参数检查、内部定义等。
这里以Junit和Google的Truth为案例展示一个测试用例案例。
定义一个Resource实体类型，实体内部定义了参数必要检查、public函数:
/**
* {@link Resource} represents a resource, which capture identifying information about the entities
* for which signals (stats or traces) are reported.
*/
@Immutable
@AutoValue
public abstract class Resource {
private static final int MAX_LENGTH = 255;
private static final String ERROR_MESSAGE_INVALID_CHARS =
" should be a ASCII string with a length greater than 0 and not exceed "
+ MAX_LENGTH
+ " characters.";
private static final String ERROR_MESSAGE_INVALID_VALUE =
" should be a ASCII string with a length not exceed " + MAX_LENGTH + " characters.";
private static final Resource EMPTY = new AutoValue_Resource(Collections.emptyMap());
Resource() {}
public static Resource getEmpty() {
return EMPTY;
}
/**
* Returns a map of labels that describe the resource.
*
* @return a map of labels.
*/
public abstract Map<String, String> getLabels();
/**
* Returns a {@link Resource}.
*
* @param labels a map of labels that describe the resource.
* @return a {@code Resource}.
* @throws NullPointerException if {@code labels} is null.
* @throws IllegalArgumentException if label key or label value is not a valid printable ASCII
* string or exceed {@link #MAX_LENGTH} characters.
*/
public static Resource create(Map<String, String> labels) {
checkLabels(labels);
return new AutoValue_Resource(labels);
}
/**
* Returns a new, merged {@link Resource} by merging the current {@code Resource} with the
* {@code other} {@code Resource}. In case of a collision, current {@code Resource} takes
* precedence.
*
* @param other the {@code Resource} that will be merged with {@code this}.
* @return the newly merged {@code Resource}.
*/
public Resource merge(@Nullable Resource other) {
if (other == null) {
return this;
}
Map<String, String> mergedLabelMap = new LinkedHashMap<>(other.getLabels());
// Labels from resource overwrite labels from otherResource.
for (Map.Entry<String, String> entry : this.getLabels().entrySet()) {
mergedLabelMap.put(entry.getKey(), entry.getValue());
}
return new AutoValue_Resource(mergedLabelMap);
}
private static void checkLabels(Map<String, String> labels) {
for (Map.Entry<String, String> entry : labels.entrySet()) {
Utils.checkArgument(
isValidAndNotEmpty(entry.getKey()), "Label key" + ERROR_MESSAGE_INVALID_CHARS);
Utils.checkArgument(
isValid(entry.getValue()), "Label value" + ERROR_MESSAGE_INVALID_VALUE);
}
}
/**
* Determines whether the given {@code String} is a valid printable ASCII string with a length not
* exceed {@link #MAX_LENGTH} characters.
*
* @param name the name to be validated.
* @return whether the name is valid.
*/
private static boolean isValid(String name) {
return name.length() <= MAX_LENGTH && StringUtils.isPrintableString(name);
}
/**
* Determines whether the given {@code String} is a valid printable ASCII string with a length
* greater than 0 and not exceed {@link #MAX_LENGTH} characters.
*
* @param name the name to be validated.
* @return whether the name is valid.
*/
private static boolean isValidAndNotEmpty(String name) {
return !name.isEmpty() && isValid(name);
}
}
为其提供高度覆盖的测试用例：
/** Unit tests for {@link Resource}. */
@RunWith(JUnit4.class)
public final class ResourceTest {
@Rule
public final ExpectedException thrown = ExpectedException.none();
private static final Resource DEFAULT_RESOURCE =
Resource.create(Collections.emptyMap());
private Resource resource1;
private Resource resource2;
@Before
public void setUp() {
Map<String, String> labelMap1 = new HashMap<>();
labelMap1.put("a", "1");
labelMap1.put("b", "2");
Map<String, String> labelMap2 = new HashMap<>();
labelMap2.put("a", "1");
labelMap2.put("b", "3");
labelMap2.put("c", "4");
resource1 = Resource.create(labelMap1);
resource2 = Resource.create(labelMap2);
}
@Test
public void create() {
Map<String, String> labelMap = new HashMap<>();
labelMap.put("a", "1");
labelMap.put("b", "2");
Resource resource = Resource.create(labelMap);
assertThat(resource.getLabels()).isNotNull();
assertThat(resource.getLabels().size()).isEqualTo(2);
assertThat(resource.getLabels()).isEqualTo(labelMap);
Resource resource1 = Resource.create(Collections.emptyMap());
assertThat(resource1.getLabels()).isNotNull();
assertThat(resource1.getLabels()).isEmpty();
}
@Test
public void testResourceEquals() {
Map<String, String> labelMap1 = new HashMap<>();
labelMap1.put("a", "1");
labelMap1.put("b", "2");
Map<String, String> labelMap2 = new HashMap<>();
labelMap2.put("a", "1");
labelMap2.put("b", "3");
labelMap2.put("c", "4");
new EqualsTester()
.addEqualityGroup(Resource.create(labelMap1), Resource.create(labelMap1))
.addEqualityGroup(Resource.create(labelMap2))
.testEquals();
}
@Test
public void testMergeResources() {
Map<String, String> expectedLabelMap = new HashMap<>();
expectedLabelMap.put("a", "1");
expectedLabelMap.put("b", "2");
expectedLabelMap.put("c", "4");
Resource resource = DEFAULT_RESOURCE.merge(resource1).merge(resource2);
assertThat(resource.getLabels()).isEqualTo(expectedLabelMap);
}
@Test
public void testMergeResources_Resource1_Null() {
Map<String, String> expectedLabelMap = new HashMap<>();
expectedLabelMap.put("a", "1");
expectedLabelMap.put("b", "3");
expectedLabelMap.put("c", "4");
Resource resource = DEFAULT_RESOURCE.merge(null).merge(resource2);
assertThat(resource.getLabels()).isEqualTo(expectedLabelMap);
}
@Test
public void testMergeResources_Resource2_Null() {
Map<String, String> expectedLabelMap = new HashMap<>();
expectedLabelMap.put("a", "1");
expectedLabelMap.put("b", "2");
Resource resource = DEFAULT_RESOURCE.merge(resource1).merge(null);
assertThat(resource.getLabels()).isEqualTo(expectedLabelMap);
}
@Test
public void testCreateResources_ArgumentKey_Null() {
Map<String, String> labelMap = new HashMap<>();
labelMap.put("a", "1");
labelMap.put(null, "2");
thrown.expect(NullPointerException.class);
Resource.create(labelMap);
}
@Test
public void testCreateResources_ArgumentKey_Unprintable() {
Map<String, String> labelMap = new HashMap<>();
labelMap.put("a", "1");
labelMap.put("\2b\3", "2");
thrown.expect(IllegalArgumentException.class);
Resource.create(labelMap);
}
}
