Cannot resolve symbol 'Assertions' <-- Error message when trying to use AssertJ in IntelliJ

Question

Similar to some other Questions, I find IntelliJ mysteriously refuses to recognize AssertJ library. I am asking again as (a) I have tried the various suggestions, and (b) I have a very simple example anyone can try themselves.

In IntelliJ 2018 and IntelliJ 2019 pre-release, I create a new project using the Maven archetype maven-archetype-quickstart version 1.4.

AssertJ 3 requires Java 8. So I changed these two lines in the POM for 1.7 to 11.

    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>

I add this to the POM:

    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
        <version>3.11.1</version>
        <scope>test</scope>
    </dependency>

Using the Maven panel in IntelliJ, I executed a clean and install.

Seems good. I verify the org.assertj:assertj-core:3.11.1 library appears in the Project panel of IntelliJ. The app runs, with Hello World appearing on the console in IntelliJ.

In the App.java file, I add this import statement.

import static org.assertj.core.api.Assertions.* ; 

Error reported in the IDE editor:

Cannot resolve symbol 'Assertions'

Some people suggest a corrupted Maven cache. So I quit IntelliJ, and I delete the .m2 folder in my home folder. I re-open my project in IntelliJ, and re-execute the Maven clean & install. Many things are downloading, so I know the Maven cache is indeed being recreated.

Yet, still the error in my editor, Cannot resolve symbol 'Assertions'.

No Java Modules involved, as the quickstart archetype has not yet been updated for that.

Answer 1

tl;dr

Change the scope element from test to compile. Or omit.

Delete <scope>test</scope>

This topic was addressed in a closed ticket # 520 on the AssertJ issue tracker.

When a Maven dependency carries a scope element with a value of test, that means you cannot use that library outside of your test-specific source package/folder.

If you are trying to call AssertJ from code in your example project’s src/main/java/… folder hierarchy, you will see that error. If you call AssertJ from src/test/java…, you will see success.

To enable AssertJ in the src/main/java/… folder hierarchy, delete the scope element in your POM dependency. So this:

    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
        <version>3.11.1</version>
        <scope>test</scope>
    </dependency>

…becomes this:

    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
        <version>3.11.1</version>
    </dependency>

Use default

Or change the scope element to the default value of compile.

    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
        <version>3.11.1</version>
        <scope>compile</scope>
    </dependency>

See the Dependency Scope section of the Maven documentation.

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FYI, the current version of assertj-core is 3.24.2 as of 2023-05.