Test fails if default value cannot be determined for a constructor or factory method\n * parameter, or if the constructor or factory method throws exception.\n *\n * @return this tester\n */\n @CanIgnoreReturnValue\n public FactoryMethodReturnValueTester testNulls() throws Exception {\n for (Invokable factory : getFactoriesToTest()) {\n Object instance = instantiate(factory);\n if (instance != null\n && packagesToTest.contains(Reflection.getPackageName(instance.getClass()))) {\n try {\n nullPointerTester.testAllPublicInstanceMethods(instance);\n } catch (AssertionError e) {\n throw new AssertionError(\"Null check failed on return value of \" + factory, e);\n }\n }\n }\n return this;\n }\n\n /**\n * Tests {@link Object#equals} and {@link Object#hashCode} against the return values of the\n * static methods, by asserting that when equal parameters are passed to the same static method,\n * the return value should also be equal; and vice versa.\n *\n *
Test fails if default value cannot be determined for a constructor or factory method\n * parameter, or if the constructor or factory method throws exception.\n *\n * @return this tester\n */\n @CanIgnoreReturnValue\n public FactoryMethodReturnValueTester testEquals() throws Exception {","sourceCodeStart":450,"sourceCodeEnd":486,"githubUrl":"https://github.com/google/guava/blob/94f39958baf7ad51ddf9c70e406ed6b188194daa/android/guava-testlib/src/com/google/common/testing/ClassSanityTester.java#L450-L486","documentation":"Thrown by ClassSanityTester.FactoryMethodReturnValueTester.testNulls() when nullPointerTester.testAllPublicInstanceMethods(instance) fails on an object returned by a static factory. The wrapping AssertionError records which factory produced the bad instance; the cause (AssertionError) describes which method failed the null-check.","triggerScenarios":"Calling ClassSanityTester.setDefault(...)/test(...)/testNulls() on a class; one of its static factory methods returns an instance whose public methods do not reject null parameters (missing @Nullable annotation + missing check).","commonSituations":"Adding a new public method that accepts parameters without null checks or @Nullable marks; auto-generating code; returning a wrapper/delegate that forwards nulls unsafely.","solutions":["Read the cause to find the failing method and parameter; add a null check (checkNotNull/requireNonNull) or annotate the parameter @Nullable if null is intentionally accepted.","Run testNulls() in isolation on the factory to iterate quickly.","Ensure every public instance method either rejects nulls explicitly or declares @Nullable on accepted-null params."],"exampleFix":"// before\npublic Foo withName(String name) {\n this.name = name.toUpperCase(); // NPE later, not at boundary\n return this;\n}\n\n// after\npublic Foo withName(String name) {\n this.name = checkNotNull(name).toUpperCase();\n return this;\n}","handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"try {\n factoryTester.testNulls();\n} catch (AssertionError e) {\n // e.getCause() is the null-pointer AssertionError naming the failing method/param\n fail(\"Factory \" + factory + \" produced an instance failing null checks: \" + e.getCause());\n}","preventionTips":["Add explicit null checks (checkNotNull/requireNonNull) or @Nullable at every public method parameter boundary.","Run ClassSanityTester.testNulls() as part of the build for every public value type."],"tags":["guava-testlib","null-checks","reflection","class-sanity"],"backgroundTag":null,"analyzedSha":"94f39958baf7ad51ddf9c70e406ed6b188194daa","analyzedAt":"2026-08-13T22:50:30.265Z","schemaVersion":2},"datasetVersion":"2026-08-14T00:17:13.853Z"}