Test frameworks & structure

@BeforeAll  static void once()   // 1x, must be static
@BeforeEach void setUp()         // before EVERY test
@Test  @DisplayName("...")
@AfterEach  void tearDown()      // runs even on failure
@AfterAll   static void end()    // 1x
@Disabled("reason")   // visible skip > commented-out

assertEquals(expected, actual);        // THAT order
assertEquals(exp, act, "msg on failure");
assertTrue(x)  assertFalse(x)  assertNotNull(x)
assertAll(
  () -> assertEquals("Products", title),
  () -> assertEquals("1", cartCount));   // reports all

@ParameterizedTest(name = "{index}: {0} -> {2}")
@CsvSource({
  "locked_out_user, secret_sauce, locked out",
  "'',              secret_sauce, Username is required"
})   // '' = empty string; quote values with commas
void invalidLogin(String u, String p, String err){...}
// needs junit-jupiter-params in pom.xml

@Tag("smoke")  @Tag("regression")
mvn test "-Dgroups=smoke"
mvn test "-DexcludedGroups=slow"
// PowerShell: quote the whole -D flag

@RegisterExtension TestWatcher w = new TestWatcher(){
  public void testFailed(ExtensionContext c, Throwable t){
    byte[] png = ((TakesScreenshot)driver)
        .getScreenshotAs(OutputType.BYTES);
    Files.write(Paths.get("screenshots", name + ".png"), png);
  }};   // field, not static; sanitize the file name

@ValueSource(strings = {"a", "b"})        one param
@CsvFileSource(resources = "/logins.csv",
               numLinesToSkip = 1)         real file
@MethodSource("myProvider")                complex objects
// files live in src/test/resources

mvn test -Dtest=LoginTest              one class
mvn test -Dtest=LoginTest#validLogin   one method
mvn test "-Dgroups=smoke"              by tag
mvn test "-Dsurefire.rerunFailingTestsCount=1"  # flaky triage

target/surefire-reports/   *.txt + TEST-*.xml
Tests run / Failures / Errors / Skipped
Failure -> app.  Error -> test.  First red block = story.