Test resources as files

[Dan Fabulich]

Consider this example repository.

https://github.com/dfabulich/file-resources-example

It has a simple App.java:

public class App 

{

    public String readFile(String path) throws Exception {

        File file = new File(path);

        FileInputStream fis = new FileInputStream(file);

        return new java.util.Scanner(fis).useDelimiter("\\A").next();

    }

}

And it has an AppTest.java.

public class AppTest

    extends TestCase

{

    public void testApp() throws Exception

    {

        String path = AppTest.class.getResource("hello.txt").getFile();

        System.out.println(path);

        App app = new App();

        assertEquals("hello", app.readFile(path));

    }

}

The repository includes a Maven pom.xml and Bazel WORKSPACE/BUILD files. The test passes when I run "mvn test", but fails when I "bazel test //:test"

In Maven, the classpath contains the exploded target/test-classes directory, so getResource("hello.txt").getFile() returns an absolute file path, suitable for use with App.java.

In Bazel, the resources are first zipped into a jar, so getResource("hello.txt').getFile() returns a jar URL string, like this:

    file:/private/var/tmp/_bazel_dfabulich/dea6568d2b91f5e0663b4131b12cb24c/file-resources-example/bazel-out/local_darwin-fastbuild/bin/test.jar!/com/redfin/hello.txt

Note the exclamation point in that path: file:/path/to/test.jar!/com/redfin/hello.txt

I suppose it was inappropriate for the test to assume that it would be run with an exploded directory on the classpath (though that assumption was correct when the test was originally written, in Maven). Nonetheless, I would like Bazel to do what Maven does, and run the tests against an exploded directory, rather than jarring the test resources up.

Is it possible to run Bazel tests in that way?

-Dan

[Alex Humesky]

One option might be to refactor the code to accept InputStreams instead of file paths as strings, and then you can do this:

public String readFile(InputStream is) throws Exception {

    return new java.util.Scanner(is).useDelimiter("\\A").next();

}

public void testApp() throws Exception

{

    URL url = AppTest.class.getResource("hello.txt").toURI().toURL();

    System.out.println(url);

    App app = new App();

    assertEquals("hello", app.readFile(url.openStream()));

}

and url.openStream() should handle files within zip files ("foo.zip!path") and regular files on the file system.

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[Ronnie R.]

If you don't want the test data file included in the jar, but prefer them to be standard files, use "data" instead of "resources".

Instead of resources=glob(['src/test/resources/**/*']),  use data=glob(['src/test/resources/**/*']),

When you execute the tests through bazle, you'll have an environment variable that points to the runfiles location.  You'll need to update your tests so to look at that path and make a decision on it being there (for Bazel) or not there (for the IDE and MVN).  Here's sample code...

private String getResource(String testfile) {

String resourceDir = "src/test/resources/";

String path = System.getenv("TEST_SRCDIR"); // Set in the Bazel wrapper

if (path == null) {

// This handles both the IDE and Maven

path = resourceDir;

} else {

// This works for Bazel

path = Paths.get(path, "/your_dir/" + resourceDir).toString();

}

return Paths.get(path, testfile).toString();

}

I find this to be very clunky, but it was the only way I could get my tests to reliably work in Maven, Bazel, and the IDE.

[Helen]

Thanks Alex and Ronnie!

I tried Ronnie's approach and it worked. The directory the resources live in is something like:

 /private/var/tmp/_bazel_helen/27683dcc4905fc6bfddcd381450719bc/main/bazel-out/local_darwin-fastbuild/bin/packagename/AllTests.runfiles/packagenamel/src/test/resources/util/img.bmp