mod: added unit tests for version constraint support

Signed-off-by: Sam Alba <samalba@users.noreply.github.com>

mod/repo_test.go

@@ -83,3 +83,36 @@ func TestListTags(t *testing.T) {
 		t.Errorf("could not list repo tags")
 	}
 }
+
+func TestVersionConstraint(t *testing.T) {
+	tmpDir, err := ioutil.TempDir("", "clone")
+	if err != nil {
+		t.Fatal("error creating tmp dir")
+	}
+	defer os.Remove(tmpDir)
+
+	r, err := clone(&Require{
+		cloneRepo: "github.com/dagger/universe",
+		clonePath: "stdlib",
+		version:   "",
+	}, tmpDir, "", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tagVersion, err := r.latestTag("<= 0.1.0")
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Make sure we select the right version based on constraint
+	if tagVersion != "v0.1.0" {
+		t.Errorf("wrong version: expected 0.1.0, got %v", tagVersion)
+	}
+
+	// Make sure an invalid constraint (version out of range) returns an error
+	_, err = r.latestTag("> 99999")
+	if err == nil {
+		t.Error("selected wrong version based on constraint")
+	}
+}