LogStream instance2 = LogStream.getInstance();

        // Each setInstance should create a new LogStream
        assertNotNull(instance1);
        assertNotNull(instance2);
        // The second setInstance replaces the first, so they should not be the same
        assertNotSame(instance1, instance2);
        // Getting instance again should return the same as instance2
        assertSame(instance2, LogStream.getInstance());
    }

	if len(pets) != 1 {
		t.Fatalf("should only find one pets, but got %v", len(pets))
	}

	CheckPet(t, pets[0], *user.Pets[0])

	if count := DB.Model(&user).Where("name = ?", user.Pets[1].Name).Association("Pets").Count(); count != 1 {
		t.Fatalf("should only find one pets, but got %v", count)
	}

	}

	// RelationModel3 should be existed
	_, err = findColumnType(&RelationModel3{}, "id")
	AssertEqual(t, nil, err)

	// RelationModel1 should not be existed
	_, err = findColumnType(&RelationModel1{}, "id")
	if err == nil {
		t.Errorf("RelationModel1 should not be migrated")
	}

	// RelationModel2 should not be existed
	_, err = findColumnType(&RelationModel2{}, "id")

    assertTrue("containsValue(present) should return true", getMap().containsValue(v0()));
  }

  public void testContains_no() {
    assertFalse("containsValue(notPresent) should return false", getMap().containsValue(v3()));
  }

  @MapFeature.Require(ALLOWS_NULL_VALUE_QUERIES)
  public void testContains_nullNotContainedButAllowed() {
    assertFalse("containsValue(null) should return false", getMap().containsValue(null));
  }

    assertTrue("contains(present) should return true", collection.contains(e0()));
  }

  public void testContains_no() {
    assertFalse("contains(notPresent) should return false", collection.contains(e3()));
  }

  @CollectionFeature.Require(ALLOWS_NULL_QUERIES)
  public void testContains_nullNotContainedButQueriesSupported() {
    assertFalse("contains(null) should return false", collection.contains(null));
  }

			}
			if c.shouldConnect() {
				should++
			}
		}
		if should < 10 {
			t.Errorf("host %q only connects to %d hosts", hosts[x], should)
		}
		t.Logf("host %q should connect to %d hosts", hosts[x], should)
	}
}

func startServer(t testing.TB, listener net.Listener, handler http.Handler) (server *httptest.Server) {
	t.Helper()
	server = httptest.NewUnstartedServer(handler)

    }

    @Test
    @DisplayName("Should get integer property with default value")
    void testGetIntWithDefault() {
        assertEquals(123, Config.getInt(testProperties, "test.int", 0));
        assertEquals(456, Config.getInt(testProperties, "nonexistent.int", 456));
        assertEquals(789, Config.getInt(testProperties, "test.invalid.int", 789));
    }

    @Test
    @DisplayName("Should get integer property")
    void testGetInt() {

        }

        // Verify lists remain valid after error
        assertNotNull(groupList, "groupList should not be null");
        assertNotNull(roleList, "roleList should not be null");
        assertNotNull(groupIdsForParentLookup, "groupIdsForParentLookup should not be null");
    }

    /**
     * Test that scheduleParentGroupLookup uses TimeoutManager correctly.

  public void testAddAllAtIndex_supportedNothing() {
    assertFalse("addAll(n, nothing) should return false", getList().addAll(0, emptyCollection()));
    expectUnchanged();
  }

  @ListFeature.Require(absent = SUPPORTS_ADD_WITH_INDEX)
  public void testAddAllAtIndex_unsupportedNothing() {
    try {
      assertFalse(
          "addAll(n, nothing) should return false or throw",
          getList().addAll(0, emptyCollection()));

In this case, you could want to document how that external API *should* look like. What *path operation* it should have, what body it should expect, what response it should return, etc.

## An app with callbacks { #an-app-with-callbacks }

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.