提高单元测试用例覆盖率

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("2円b3円", "2");
 thrown.expect(IllegalArgumentException.class);
 Resource.create(labelMap);
 }
}

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