tests: Add a gjs-based test

This covers introspection, and in general is a much better way to get
API coverage tests.

tests/test-core.js

@@ -0,0 +1,38 @@
+#!/usr/bin/env gjs
+
+const Gio = imports.gi.Gio;
+const OSTree = imports.gi.OSTree;
+
+function assertEquals(a, b) {
+    if (a != b)
+	throw new Error("assertion failed " + JSON.stringify(a) + " == " + JSON.stringify(b));
+}
+
+let testDataDir = Gio.File.new_for_path('test-data');
+testDataDir.make_directory(null);
+testDataDir.get_child('some-file').replace_contents("hello world!", null, false, 0, null);
+
+let repoPath = Gio.File.new_for_path('repo');
+let repo = OSTree.Repo.new(repoPath);
+repo.create(OSTree.RepoMode.ARCHIVE_Z2, null);
+
+repo.open(null);
+
+assertEquals(repo.get_mode(), OSTree.RepoMode.ARCHIVE_Z2);
+
+repo.prepare_transaction(null);
+
+let mtree = OSTree.MutableTree.new();
+repo.write_directory_to_mtree(testDataDir, mtree, null, null);
+let [,dirTree] = repo.write_mtree(mtree, null);
+let [,commit] = repo.write_commit(null, 'Some subject', 'Some body', null, dirTree, null);
+print("commit => " + commit);
+
+repo.commit_transaction(null, null);
+
+let [,root,checksum] = repo.read_commit(commit, null);
+let child = root.get_child('some-file');
+let info = child.query_info("standard::name,standard::type,standard::size", 0, null);
+assertEquals(info.get_size(), 12);
+
+print("test-core complete");