add minimal test for 'pkg/loader' + update loader to let 'lsb_release -is' command for its caller

internal/pkg/loader.go

@@ -6,24 +6,15 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"strings"
 )
 
 var ErrUnknownDistribution = errors.New("unknown linux distribution")
 var ErrNoCandidateInstalled = errors.New("no package-manager candidate installed")
 var ErrNoDriverFound = errors.New("no driver found for the package manager")
 
-func Load() (PackageManager, error) {
+func Load(_distro string) (PackageManager, error) {
 
-	// 1. get distro name
-	out, err := exec.Command("lsb_release", "-is").Output()
-	if err != nil {
-		return nil, err
-	}
-
-	distro := strings.ToLower(strings.Trim(string(out), " \n\t"))
-
-	// 2. load config file
+	// 1. load config file
 	driverTable := filepath.Join(os.Getenv("GOPATH"), "src/git.xdrm.io/xdrm-brackets/nix-amer/meta/pkg-drivers.json")
 	file, err := os.Open(driverTable)
 	if err != nil {
@@ -31,7 +22,7 @@ func Load() (PackageManager, error) {
 	}
 	defer file.Close()
 
-	// 3. Parse json
+	// 2. Parse json
 	table := make(map[string][]string)
 	decoder := json.NewDecoder(file)
 	if err := decoder.Decode(&table); err != nil {
@@ -39,13 +30,13 @@ func Load() (PackageManager, error) {
 	}
 	decoder = nil
 
-	// 4. Get available package-manager list for distro
-	available, exists := table[distro]
+	// 3. Get available package-manager list for distro
+	available, exists := table[_distro]
 	if !exists || len(available) < 1 {
 		return nil, ErrUnknownDistribution
 	}
 
-	// 5. Check each available package-manager in order
+	// 4. Check each available package-manager in order
 	selected := ""
 	for _, current := range available {
 		if exec.Command("which", current).Run() == nil {
@@ -59,7 +50,7 @@ func Load() (PackageManager, error) {
 		return nil, ErrNoCandidateInstalled
 	}
 
-	// 6. Instanciate
+	// 5. Instanciate
 	switch selected {
 	case "apt-get":
 		return new(Apt), nil

internal/pkg/loader_test.go

@@ -0,0 +1,47 @@
+package pkg
+
+import (
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+func TestUnknownDistribution(t *testing.T) {
+
+	_, err := Load("invalid-distro-xxx")
+	if err != ErrUnknownDistribution {
+		t.Errorf("expected <%s>, got <%s>", ErrUnknownDistribution, err)
+		t.Fail()
+	}
+
+}
+func TestNoCandidateInstalled(t *testing.T) {
+
+	// get host distro
+	out, err := exec.Command("lsb_release", "-is").Output()
+	if err != nil {
+		t.Errorf("cannot get host linux distribution")
+		t.Fail()
+	}
+	hostDistro := strings.ToLower(strings.Trim(string(out), " \n\t"))
+
+	// valid candidate
+	_, err = Load(hostDistro)
+	if err != nil {
+		t.Errorf("expected <nil>, got <%s>", err)
+		t.Fail()
+	}
+
+	// invalid candidate
+	distro := "solus"
+	if hostDistro == distro {
+		distro = "ubuntu"
+	}
+
+	_, err = Load(distro)
+	if err != ErrNoCandidateInstalled {
+		t.Errorf("expected <%s>, got <%s>", ErrNoCandidateInstalled, err)
+		t.Fail()
+	}
+
+}