Diffblue Logo
Go to diffblue.com

Get unit tests for your Java code automatically with our free IntelliJ plugin. Download now

Knowledge Base > Troubleshooting > Output codes

Output codes

Meaning of Diffblue Cover output codes.

The possible codes are described below:

Environment codes

Code Meaning Example Suggestion
E001 Failed to insert a test into the created test Java file Please enable read and write permissions on file SomeJavaFile.java and its parent folder.
E002 Failed to overwrite the created test Java file Please enable read and write permissions on file SomeJavaFile.java and its parent folder.
E003 Failed to read the existing test Java file Please enable read permissions on file SomeJavaFile.java and its parent folder.
E010 JUnit dependencies version mismatch Diffblue Cover may produce non-passing tests because the build system configuration contains mismatching versions of junit-platform-commons and junit-jupiter-api. Please see the prerequisite information.
E011 Test validation command failed Diffblue Cover may produce non-passing tests because running the validation command failed.

Please see the information on validation. You may also find information on output code V003 useful.
E012 Failed to execute the existing tests An error occurred when using the build system to execute the existing tests. This will prevent Diffblue Cover from validating the created tests or even creating them.
E013 Failed to create test Java file Please enable read and write permissions on the  folder listed.
E014 Required dependency not found Diffblue Cover could not start because a required dependency could not be found. Make sure that all required dependencies are installed in paths where Diffblue Cover can find them.
E015 Failed to download junit-platform-launcher artifact Diffblue Cover may produce non-passing tests because it failed to download a junit-platform-launcher-artifact due to an exception. Make sure that this artifact can be downloaded from the relevant URL. Please see Working with code E015 for further details.
E016 Failed to connect to analysis service Make sure that local firewall settings allow connecting to a service at HOST:PORT.
E019 Failed to create Spring context Attempted to initialize test context using a class someClass but threw an exception.
E020 Failed to start up analysis service Please see Working with code E020.
E045 Validation command failed for unknown reasons Cover tried and failed to validate the tests it generated. The output from running this command is available in the log file, see the last lines of the log file. While Cover could not figure out the reason for this and cannot fix it automatically, this issue is usually due to an incorrect validation command, or due to the failure of existing, user-provided tests.
E047 Unsupported Java version Please use Java 8 or Java 11 (but not version 11.0.7).
E048 Current JVM does not support JDK which compiled the project Diffblue Cover is running on one JVM version, but your project was built with another JDK version. Diffblue Cover needs to be executed with the same or a more recent Java version than the version with which the project was compiled. The following classes were compiled with an old JDK version: (list of classes). Either recompile the project with Java version that Diffblue Cover is running in, or run Diffblue Cover with JVM version that you used to compile the project. Please also see the prerequisite information.
E049 inotify limit too low Try restarting the IDE and/or your machine. Check your inotify limit with sudo sysctl fs.inotify.max_user_watches, try setting it to a higher value with sudo sysctl fs.inotify.max_user_watches=<new-value>. You can make this change permanent by following the instructions on JetBrains website.
E050 Unsupported Tool Version Found tool  at version but requiredVersion is required.
E051 Current JVM does not support the JDK which compiled the project Diffblue Cover is running on JVM version {0}, but your project was built with JDK version {1}. Diffblue Cover needs to be executed with the same or a more recent Java version than the version with which the project was compiled.
E052 Missing or unsupported test dependency The following test dependencies were not found, or were found at an unsupported version. Please add the following dependencies to your project: (list).
E053 Missing or unsupported JUnit dependency A supported JUnit dependency was not found, or was found at an unsupported version. Please ensure that you have a supported version of JUnit as a test dependency. Supported versions include JUnit 4.7 - 4.13, or 5.0 - 5.7. For example, use one of the following dependencies: (list).
E054 No class files found Diffblue Cover could not find any .class files for your project. This usually indicates that your project has not yet been compiled.For Maven, run mvn install -DskipTests from the root of the project.For Gradle, run gradle :compileJava from the root of the project.Depending on your project setup, additional configuration may be required.
E055 Failed to compile a simple example test Diffblue Cover tried to compile a simple example test to help it figure out the right project configuration, but the test failed to compile when running a validation command.
E056 JDK not found Diffblue Cover requires a JDK to run. A JRE is not sufficient. Diffblue Cover expects the JDK in RT_JAR_PATH or JMODS_PATH. Make sure a JDK is installed in these locations.
E057 Service startup certificate problem There was a problem with the SSL certificates used to set up the connection. Check whether you have the full set of CA certificates for Java installed.
E058 Service startup I/O problem  There was an I/O problem while trying to set up a network connection to the service. Please check whether you have a firewall configuration that disallows TCP servers on localhost.
E059 Service startup message timeout Diffblue Cover did not receive the “port message” from the service after waiting for the timeout. If your machine is heavily loaded or very slow, try reducing load before running Cover.
E060 Service startup SSL problem There was a problem with the SSL connection to the service. Please report this to Diffblue.
E061 Service startup timeout Diffblue Cover did not receive the “alive message” from the service after waiting for the timeout. If your machine is heavily loaded or very slow, try reducing load before running Cover.
E062 Service JVM exited unexpectedly  Please contact Diffblue: (https://www.diffblue.com/support).
E063 Diffblue Cover component missing  Diffblue Cover consists of several different components that are needed to produce test cases. 
E064 Service startup I/O failure  Starting up the service failed because of an I/O problem while trying to execute the JVM for the service process.  Please check whether your installation  is complete, whether  all files are readable and whether the JVM in JAVA_HOME is executable.
E065 Service startup interrupted Please report this to Diffblue.
E066 Dependency incompatible with JDK The following supported dependencies were not found or were incompatible with the current JDK (version). Please add the following Gradle dependencies to your project: (list). Please add the following Maven dependencies to your project: (list).
E067 JVM not a 64-bit implementation Diffblue Cover requires a 64-bit JDK to run. A 32-bit JVM is not sufficient.

Failure codes

Code Meaning Example Suggestion
F001 Internal Error Failed to close a class loader. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.
F002 Internal Error Failed to execute test. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.
F003 Internal Error Failed to execute test. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.
F004 Internal Error Failed to execute test. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.
F009 Internal Error Failed to execute test. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.
F018 Internal Error Failed to extract inputs from recorded execution trace. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.

Reason codes (reasons for tests not being created that may have a work around)

Code Meaning Example Suggestion
R002 Missing observers Diffblue Cover was unable to create an assertion. Add getters for the following fields or make them package-private: (list of fields).
R004 No meaningful assertions found Diffblue Cover was unable to create an assertion. Make sure that fields modified by the MUT have package-private, protected or public getters. Please see Working with code R004 for further details.
R005 Unable to load class Please check that someClass is available on your test runtime classpath.
R006 Static initializer failed The static initializer of someClass threw an exception while trying to load it. Make sure the static initializer of someClass can be executed without throwing exceptions.
R007 Class not accessible Diffblue Cover was unable to construct an instance of someClass. Make one of the following constructors or factory methods package-private: (list of constructors).
R008 Failed to instantiate class under test Diffblue Cover was unable to construct an instance of someClass. Add a package-visible constructor or a factory method for testing which (ideally) takes no arguments, and does not throw, return null or return a subtype.
R010 Timeout Creating the arrange/act section of your test took a long time. This often happens because Diffblue Cover ran code in your project which requests user input (System.in), blocks on a lock, or runs into an infinite or very long loop. Please see Working with code R010 for further details.
R011 Sandboxing policy violation Diffblue Cover ran code in your project that tried to violate the sandboxing policy. Diffblue Cover’s default sandboxing policy disallows this in order to prevent your system from overwriting your files or opening network connections. Please see Working with code R011 for further details.
R013 No inputs found that don’t throw a trivial exception Diffblue Cover tried to run the following arrange/act section, but it threw a trivial exception. Add constructors or factory methods that make it easier to construct objects of the following classes in order to prevent someMethod() from throwing an exception. Please see Working with code R013 for further details.
R015 Method under test may be nondeterministic Diffblue Cover tried to run the following test twice, but it first passed the assertions and then failed. Please see Working with code R015 for further details.
R019 Method not in trace Record your program again and provide program inputs that trigger at least one call of the method someMethod().
R020 Temporary files not cleaned up The method under test created temporary files without deleting them: (list of files). Please ensure that temporary files are deleted after use.
R021 Missing Spring component Diffblue Cover detected Spring on the classpath, but is missing critical classes to load the Spring context: someClasses.
R022 Failed to load trace file Continuing with the loaded fragment of the trace. Record your program again. If the problem persists please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.
R024 Out of resources Diffblue Cover failed to create tests for method someMethod() because its execution seems to exceed available resources (memory, threads, file handles, etc).
R025 Skipped due to previous failure Diffblue Cover failed to create tests for someMethod() and thus skipped all methods in class someClass.
R026 Failed to create Spring context Attempted to initialize test context using a class someClass but threw an exception.
R027 Failed to load Spring Boot application context Diffblue Cover may not be able to produce tests for methods invoked by Spring.
R028 Incomplete repository information Diffblue Cover is unable to create tests for a Spring Data Repository because necessary information was not available.

Testability codes

Code Meaning Suggestion
T001 Trivial getter Information only.
T002 Trivial setter Information only.
T003 Private method The method is declared private or in a private inner class. It cannot be called from another class in the same package. Diffblue Cover will attempt to test it indirectly through other callable methods. If you want to test this method directly make it package-private.
T004 In anonymous inner class The method is declared in an anonymous inner class. It cannot be called directly. Diffblue Cover will attempt to test it indirectly through other callable methods. If you want to test this method directly factor out the anonymous class into a package-private class.
T005 Trivial constructor Information only.
T006 Main method It is difficult to assert on side effects of main methods in a unit test. Refactor the main method, e.g. factor out its body into a separate, accessible method that returns the results that should be asserted on.
T007 Framework configuration callbacks Certain framework callbacks (e.g. Spring’s @InitBinder) should not be directly tested because they have side effects. Diffblue Cover will attempt to test it indirectly through other callable methods.
T008 Private and never called The method cannot be called from another class in the same package. It is not called by any other method and therefore cannot be tested. If this method is called by reflection then annotate it with @SuppressWarnings("unused"). If the method is indeed dead code then remove it from your code base.
T009 Non-abstract instance method in abstract class It will be tested by testing an implementation of the abstract class.
T010 Abstract or interface method Information only.
T011 The method is annotated @SuppressWarnings ("unused") The method is declared private and annotated with @SuppressWarnings(\"unused\"). This indicates that the method is probably called by reflection. The method will not be tested directly. If you want to test this method directly then make it package-private and remove the annotation.
T020 Other trivial method Information only.
T021 Empty method body Information only.
T022 Cannot test mocked method The method is not unit-testable because it must be mocked.

Validation codes

Code Meaning Suggestion
V003 Test discarded during validation Please see Working with code V003 for further details.

W (Verification) codes

Code Meaning Suggestion
W001 Test did not compile Diffblue Cover removed the following test because it did not compile. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.
W002 Test compiled but did not pass Diffblue Cover removed the following test because it did not pass when run. Please contact Diffblue through the appropriate support channel (https://www.diffblue.com/support) providing details about this error.