| R000 | Success. Test compiled and passed during verification. | N/A |
| R002 | Nothing to assert: the constructed class doesn’t have observer methods. Observer methods are parameterless, read-only methods that return the state of the class; for instance, getters, size(), toString(). | Add getter methods to the constructed class. |
| R003 | Nothing to assert: the return/parameter types of the method under test don’t have observer methods. Observer methods are parameterless, read-only methods that return the state of the class; for instance, getters, size(), toString(). | Add observer methods to the parameter/return types of the method. |
| R004 | Unable to find any meaningful assertion. | Add getter methods in the parameter/return class types of the method under test that access or return fields written by the method under test. This error could also happen because good inputs for the method under test could not be determined. |
| R005 | Unable to load class "X". Loading the class failed (probably because it was not present in the classpath), but it is needed to generate the test. | Check that your classpath is complete; in particular, check that you do not have any dependency exclusions configured. |
| R006 | Unable to load class "X": static initializer failed. The static initializers of the class threw an exception while trying to load it. Diffblue Cover needs to load the class to generate a test. | Check that the class can be loaded without any errors in the environment where you create and run your tests. |
| R007 | Unable to instantiate class “X”: no accessible constructor or factory method. Diffblue Cover needs to construct an instance of “X” but we could not find any accessible constructors or factory methods. | Provide a package-visible constructor or factory method for testing that, ideally, takes no arguments and does not throw, return null or return a subtype. |
| R008 | Unable to instantiate class X containing the method under test. Diffblue Cover was not able to instantiate the class using accessible constructors or factory methods. We aborted because the method under test lives in this class, or a nested class. | As R007. |
| R010 | Timeout while generating the arrange/act section of your test. Generating the arrange/act sections of your test took more than X seconds. This often happens because we ran code in your project which requests user input (System.in), implements a service loop, or runs into an infinite (or very long) loop. | N/A |
| R011 | Attempt to “X” broke the sandboxing policy. To generate tests we execute your code in a sandboxed environment which, by default, prevents things like overwriting your files or opening network connections. Your code tried to break the current sandboxing policy, so we aborted. | N/A |
| R012 | User code failed badly by throwing a “X”. When trying to execute some of your code, we received a particularly serious error “X” (an instance of LinkageError or VirtualMachineError). One possible reason is that initializing a class failed due to timeouts or sandboxing at some point, so later instantiation attempts of this class will fail with an error. Stack trace:… | This will require debugging why your code caused the error; possible mitigations may include modifying the sandboxing policy or increasing timeouts, or changes to your code to make it easier to test. |
| R013 | Unable to generate test inputs not throwing a trivial exception: “X”. We failed to find inputs to the method under test which would NOT lead to throwing of a trivial exception, like NullPointerException or LinkageError. | Please see the separate article: Working with code R013. |
| R014 | Could not start test generator because “X” could not be found. We could not start the test generator because “X”, which is documented as a requirement for test case generation, could not be found. | Make sure that all required dependencies (JDK, …) are installed in paths where Diffblue Cover can find them. |
| R015 | Test replay failed. A test was generated but immediately failed one or more assertions, probably because the method under test is stateful or nondeterministic. | Try splitting stateful or nondeterministic methods into stateless and deterministic parts where the state or nondeterminism is injected via a parameter. |
| R016 | Current JVM 8 does not support the JDK 11 which compiled the project. Diffblue Cover is running on JVM version 8, but the project being analyzed was built with JDK version 11. Diffblue Cover needs to be executed with the same or a more recent Java version that the version with which the project was compiled. | Either recompile the project with Java version 8 (or older), or run Diffblue Cover with JVM version 11 (or a more recent Java version). For DCover CLI 3.0 users only, ensure that your JAVA_HOME or the first java executable in your PATH environment variable is the same or a more recent version than Java 11 (the project Java version). |
| R017 | Unable to create any tests that do not assert on a thrown exception. If only exception test cases are created for a particular method, tests are then discarded as testing only exceptions is not considered to be valuable test coverage and can provide false confidence. | Diffblue Cover could not determine valid inputs for the methods under test. Please ensure factories are added for the input types. |
| R020 | Temporary files were created but not deleted. | Ensure that the method under test, or any method called by the method under test, deletes any temporary files created. These must be deleted before the method under test completes. |
| R021 | Missing Spring components. In order to generate Spring tests, Diffblue Cover needs several Spring classes and resources on its classpath. | Ensure that your Spring project can execute a trivial Spring controller unit test in its test configuration. |
