Add test for docker environment variable behavior

pkg/docker/docker_test.go

@@ -0,0 +1,72 @@
+package docker
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestLoadEnvVars(t *testing.T) {
+	tempDir, err := ioutil.TempDir("", "test_load_env_vars")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	podEnvDir := filepath.Join(tempDir, "pod")
+	launchableEnvDir := filepath.Join(tempDir, "launchable")
+	err = os.Mkdir(podEnvDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.Mkdir(launchableEnvDir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = ioutil.WriteFile(filepath.Join(podEnvDir, "OVERRIDE"), []byte("not_overridden"), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = ioutil.WriteFile(filepath.Join(launchableEnvDir, "OVERRIDE"), []byte("overridden"), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = ioutil.WriteFile(filepath.Join(launchableEnvDir, "LAUNCHABLE_ONLY"), []byte("whatever"), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = ioutil.WriteFile(filepath.Join(podEnvDir, "POD_ONLY"), []byte("whatever"), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	envVars, err := loadEnvVars(podEnvDir, launchableEnvDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(envVars) != 3 {
+		t.Fatalf("expected 3 env vars but there were %d", len(envVars))
+	}
+
+	if !contains(envVars, "OVERRIDE=overridden") {
+		t.Errorf("expected to find OVERRIDE=overridden in the environment variables because the launchable one should override the pod one, found %s", envVars)
+	}
+	if !contains(envVars, "POD_ONLY=whatever") {
+		t.Errorf("expected to find POD_ONLY=whatever in the environment variables because the launchable one should override the pod one, found %s", envVars)
+	}
+	if !contains(envVars, "LAUNCHABLE_ONLY=whatever") {
+		t.Errorf("expected to find LAUNCHABLE_ONLY=whatever in the environment variables because the launchable one should override the pod one, found %s", envVars)
+	}
+}
+
+func contains(set []string, val string) bool {
+	for _, s := range set {
+		if s == val {
+			return true
+		}
+	}
+
+	return false
+}