断言
断言的基本原理和意图隐藏在无意义的单词和数字背后，难以理解，难以验证断言的正确性。
Bad eg.
@Test
public void outputHasLineNumbers() {String content = "1st match on #1\nand\n2nd match on #3";String out = grep.grep("match", "test.txt", content);assertTrue(out.indexOf("test.txt:1 1st match") != -1);assertTrue(out.indexOf("test.txt:3 2nd match") != -1);
}Good eg.
@Test
public void outputHasLineNumbers() {String content = "1st match on #1\nand\n2nd match on #3";String out = grep.grep("match", "test.txt", content);assertThat(out, containsString("test.txt:1 1st match"));assertThat(out, containsString("test.txt:3 2nd match"));
}一个测试应该只有一个失败的原因
按位
Bad eg.
@Test
public void platformBitLength() {assertTrue(Platform.IS_32_BIT ^ Platform.IS_64_BIT);
}Good eg.
@Test
public void platformBitLength() {assertTrue("Not 32 or 64-bit platform?", Platform.IS_32_BIT || Platform.IS_64_BIT);assertFalse("Cant't be 32 and 64-bit at the same time." Platform.IS_32_BIT && Platform.IS_64_BIT);
}附加细节
数据初始化+断言细节--混在一起
Bad eg.
public class TestObjectSpace {private Ruby runtime;private ObjectSpace objectSpace;@Beforepublic void setUp() {runtime = Ruby.newInstance();objectSpace = new ObjectSpace();}@Testpublic void testObjectSpace() {IRubyObject o1 = runtime.newFixnum(10);IRubyObject o2 = runtime.newFixnum(20);IRubyObject o3 = runtime.newFixnum(30);IRubyObject o4 = runtime.newString("hello");objectSpace.add(o1);objectSpace.add(o2);objectSpace.add(o3);objectSpace.add(o4);List storedFixnums = new ArrayList(3);storedFixnums.add(o1);storedFixnums.add(o2);storedFixnums.add(o3);Iterator strings = objectSpace.iterator(runtime.getString());assertSame(o4, strings.text());assertNull(strings.next());Iterator numerics = objectSpace.iterator(runtime.getNumeric());for(int i=0; i<3; i++) {Object item = numerics.next();assertTrue(storedFixnums.contains(item));}assertNull(numerics.next());}
}Good eg.
public class TestObjectSpace {private Ruby runtime;private ObjectSpace objectSpace;private IRubyObject string;private List<IRubyObject> fixnums;@Beforepublic void setUp() {runtime = Ruby.newInstance();objectSpace = new ObjectSpace();string = runtime.newString("hello");fixnums = new ArrayList<IRubyObject>() {{add(runtime.newFixnum(10));add(runtime.newFixnum(20));add(runtime.newFixnum(30));}};}@Testpublic void testObjectSpace() {//填充ObjectSpaceaddTo(space, string);addTo(space, fixnums)//检查ObjectSpace的内容Iterator strings = space.iterator(runtime.getString());assertContainsExactly(strings, string);Iterator numerics = space.iterator(runtime.getNumeric());assertContainsExactly(numerics, fixnums);}private void addTo(ObjectSpace space, Object... values) {}private void addTo(ObjectSpace space, List values) {}private void assertContainsExactly(Iterator i, Object... values) {}private void assertContainsExactly(Iterator i, List values){}
}方法粒度
人格分裂：一个测试方法内有多个测试。
Bad eg.
@Test
public void testParsingCommandLineArguments() {String[] args = {"-f", "hello.txt", "-v", "--version"};Configuration config = new Configuration();config.processArguments(args);assertEquals("hello.txt", config.getFileName());assertFalse(config.isDebuggingEnabled());assertFalse(config.isWarningsEnabled());assertTrue(config.isVerbose());assertTrue(config.shouldShowVersion());config = new Configuration();try {config.processArguments(new String[] {"-f"});fail("Should've faild");} catch (InvalidArgumentException e) {// this is okay and expected}
}Good eg.
public class TestConfiguration {private Configuration config;@Beforepublic void before() {config = new Configuration();}@Testpublic void validArgumentsProvided() {String[] args = {"-f", "hello.txt", "-v", "--version"};config.processArguments(args);assertEquals("hello.txt", config.getFileName());assertFalse(config.isDebuggingEnabled());assertFalse(config.isWarningsEnabled());assertTrue(config.isVerbose());assertTrue(config.shouldShowVersion());}@Test(expected = InvalidArgumentException.class)public void missingArgument() {config.processArguments(new String[] {"-f"});}
}逻辑分割
过度分散，增加认知负担。
Bad eg.
public class TestRuby {private Ruby runtime;@Beforepublic void before() {runtime = Ruby.newInstance();}@Testpublic void testVarAndMet() {runtime.getLoadService().init(new ArrayList());eval("load 'test/testVariableAndMethod.rb'");assertEquals("Hello World", eval("puts($a)"));assertEquals("dlroW olleH", eval("puts($b)"));assertEquals("Hello World", eval("puts $d.reverse, $c, $e.reverse"));assertEquals("135 20 3", eval("put $f, \" \", $g, \" \", $h"));}
}代码与文件分离testVariableAndMethod.rb
a = String.new("Hello World");
b = a.reverse
c = " "
d = "Hello".reverse
e = a[6, 5].reverse
f = 100 + 35
g = 2 * 10
h = 13 % 5
$a = a
$b = b
$c = c
$d = d
$e = e
$f = f
$g = g
$h = h
Good eg.
public class TestRuby {private Ruby runtime;private AppendableFile script;@Beforepublic void before() {runtime = Ruby.newInstance();script = withTempFile();}@Testpublic void variableAssignment() {script.line("a = String.new('Hello')");script.line("b = 'World'");script.line("$c = 1 + 2");afterEvaluating(script);assertEquals("Hello", eval("puts(a)"));assertEquals("World", eval("puts b"));assertEquals("3", eval("puts $c"));}@Testpublic void methodInvocation() {script.line("a = 'Hello'.reverse");script.line("b = 'Hello'.length()");script.line("c = ' abc '.trim(' ', '_')");afterEvaluating(script);assertEquals("olleH", eval("puts a"));assertEquals("3", eval("puts b"));assertEquals("_abc_", eval("puts c"));}private void afterEvaluating(AppendableFile sourceFile) {eval("load '" + sourceFile.getAbsolutePath() + "'");}
}魔法数字
Bad eg.
public class BowlingGameTest {@Testpublic void perfectGame() {roll(10, 12);assertThat(game.score(), is(equalTo(300)));}}Good eg.
public class BowlingGameTest {@Testpublic void perfectGame() {roll(pins(10), times(12));assertThat(game.score(), is(equalTo(300)));}private int pins(int n) {return n;}private int times(int n) {return n;}
}
冗长安装
Bad eg.
public class PackageFetcherTest {private PackageFetcher fetcher;private Map downloads;private File tempDir;@Beforepublic void before() {String systemTempDir = System.getProperty("java.io.tmpdir");tempDir = new File(systemTempDir, "downloads");tempDir.mkDirs();String filename = "/manifest.xml";InputStream xml = getClass().getResourceAsStream(filename);Document manifest = XOM.parse(IO.streamAsString(xml));PresentationList presentations = new PresentationList();presentations.parse(manifest.getRootElement());PresentationStorage db = new PresentationStorage();List list = presentations.getResourcesMissingFrom(null, db);fetcher = new PackageFetcher();downloads = fetcher.extractDownloads(list);}@Afterpublic void after() {IO.delete(tempDir);}@Testpublic void downloadsAllResources() {fetcher.download(downloads, tempDir, new MockConnector());assertEquals(4, tempDir.list().length);}
}Good eg.
public class PackageFetcherTest {private PackageFetcher fetcher;private Map downloads;private File tempDir;@Beforepublic void before() {fetcher = new PackageFetcher();tempDir = new File(systemTempDir, "downloads");downloads = extractMissingDownloadsFrom("/manifest.xml");}@Afterpublic void after() {IO.delete(tempDir);}@Testpublic void downloadsAllResources() {fetcher.download(downloads, tempDir, new MockConnector());assertEquals(4, tempDir.list().length);}private File createTempDir(String name) {String systemTempDir = System.getProperty("java.io.tmpdir");File dir = new File(systemTempDir, name);dir.mkDirs();return dir;}private Map extractMissingDownloadsFrom(String path) {PresentationStorage db = new PresentationStorage();List list = presentations.createPresentationListFrom(path);List downloads = list.getResourcesMissingFrom(null, db);return fetcher.extractDownloads(downloads);}private PresentationList createPresentationListFrom(String path) {PresentationList presentations = new PresentationList();presentations.parse(readManifestFrom(path).getRootElement());}private Document readManifestFrom(String path) {InputStream xml = getClass().getResourceAsStream(path);Document manifest = XOM.parse(IO.streamAsString(xml));}
}过度保护
Bad eg.
@Test
public void count() {Data data = project.getData();assertNotNull(data);//过度保护，没必要assertEquals(4, data.count());
}Good eg.
@Test
public void count() {Data data = project.getData();assertEquals(4, data.count());
}
