Import cannot be resolved by test plugin fragment using Tycho but works in Eclipse

Question

I have a plugin project which I am trying to create a test plugin for. The packages in my plugin project are available to other plugins in my workspace, including the test plugin, but when I try and build my projects using tycho the test plugin is throwing an error stating that the import cannot be resolved.

[ERROR] Failed to execute goal org.eclipse.tycho:tycho-compiler-plugin:0.25.0:compile (default-compile) on project REDACTED.tests: Compilation failure: Compilation failure:
[ERROR] REDACTED/PlanImportTest.java:[7]
[ERROR] import REDACTED.pluginname.Argument;
[ERROR] ^^^^^^^^^^^^
[ERROR] The import REDACTED.pluginname cannot be resolved

I am new to Tycho so I think there is probably an issue with my project layout, but I can't find a solution to my problem online. Does anyone know why this import is working in eclipse but not when running a maven/tycho build on the command line? Relevant files below.

Plugin manifest:

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: REDACTED.pluginname
Bundle-SymbolicName: REDACTED.pluginname;singleton:=true
Bundle-Version: 1.0.0.qualifier
Export-Package: REDACTED
Bundle-RequiredExecutionEnvironment: JavaSE-1.8
Eclipse-BuddyPolicy: registered
Eclipse-RegisterBuddy: REDACTED

Plugin POM:

<project>
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>REDACTED</groupId>
        <artifactId>REDACTED</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>REDACTED</relativePath>
    </parent>
    <groupId>REDACTED</groupId>
    <artifactId>REDACTED.pluginname</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>eclipse-plugin</packaging>
</project>

Test class

import static org.junit.Assert.*;
import org.junit.Test;
import REDACTED.pluginname.Argument;

public class PlanImportTest {

    @Test
    public void test() {
        Argument a = null;
        assertTrue(true);
    }
}

Test project manifest:

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: REDACTED
Bundle-SymbolicName: REDACTED.tests
Bundle-Version: 1.0.0.qualifier
Bundle-Vendor: REDACTED
Fragment-Host: REDACTED.pluginname;bundle-version="1.0.0.qualifier"
Bundle-RequiredExecutionEnvironment: JavaSE-1.8
Require-Bundle: org.junit;bundle-version="4.12.0"

Test project POM:

<project>
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>REDACTED</groupId>
        <artifactId>REDACTED</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>REDACTED</relativePath>
    </parent>
    <groupId>REDACTED</groupId>
    <artifactId>REDACTED.tests</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>eclipse-test-plugin</packaging>
    <build>
        <plugins>
            <plugin>
                <groupId>org.eclipse.tycho</groupId>
                <artifactId>tycho-surefire-plugin</artifactId>
                <configuration>
                    <testClass>REDACTED.Test</testClass>
                    <dependencies>
                        <dependency>
                            <type>eclipse-plugin</type>
                            <groupId>REDACTED</groupId>
                            <artifactId>REDACTED.pluginname</artifactId>
                            <version>1.0.0-SNAPSHOT</version>
                        </dependency>
                    </dependencies>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Answer 1

It turns out the problem was that my plugin to be tested was not exporting the source directory correctly. A change to the build.properties file fixed this:

Before:

bin.includes = META-INF/,\
               src/
output.. = bin

After:

bin.includes = META-INF/,\
               src/
source.. = src
output.. = bin

So simple but I got there in the end.