I created a suite with two modules. First one had

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://www.netbeans.org/ns/project/1">
    <type>org.netbeans.modules.apisupport.project</type>
    <configuration>
        <data xmlns="http://www.netbeans.org/ns/nb-module-project/2">
            <code-name-base>org.yourorghere.module1</code-name-base>
            <suite-component/>
            <module-dependencies>
                <dependency>
                    <code-name-base>org.openide.actions</code-name-base>
                    <build-prerequisite/>
                    <compile-dependency/>
                    <run-dependency>
                        <specification-version>6.6.0.1</specification-version>
                    </run-dependency>
                </dependency>
            </module-dependencies>
            <public-packages/>
        </data>
    </configuration>
</project>

and contained

module1/test/unit/src/module1test/Foo.java:
package module1test;
public class Foo {
    public Foo() {
    }
}

Second one had

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://www.netbeans.org/ns/project/1">
    <type>org.netbeans.modules.apisupport.project</type>
    <configuration>
        <data xmlns="http://www.netbeans.org/ns/nb-module-project/3">
            <code-name-base>org.yourorghere.module2</code-name-base>
            <suite-component/>
            <module-dependencies>
                <dependency>
                   
<code-name-base>org.netbeans.libs.commons_logging</code-name-base>
                    <build-prerequisite/>
                    <compile-dependency/>
                    <run-dependency>
                        <release-version>1</release-version>
                        <specification-version>1.4</specification-version>
                    </run-dependency>
                </dependency>
            </module-dependencies>
            <test-dependencies>
                <test-type>
                    <name>unit</name>
                    <test-dependency>
                        <code-name-base>org.yourorghere.module1</code-name-base>
                        <compile-dependency/>
                        <test/>
                    </test-dependency>
                </test-type>
            </test-dependencies>
            <public-packages/>
        </data>
    </configuration>
</project>

and contained

module2/test/unit/src/module2test/Bar.java:
package module2test;
public class Bar {
    public Bar() {
        new module1test.Foo();
    }
}

The usage of Foo from Bar is marked as an error in the editor; and Bar.java
cannot be built, even after module1's tests are built as

module1/build/test/unit/dist/tests.jar