Restructure main

Add more tests

Signed-off-by: Christopher Meis <christopher.meis@9elements.com>

cmds/core/cat/cat.go

@@ -16,6 +16,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"io"
 	"log"
 	"os"
@@ -25,36 +26,41 @@ var (
 	_ = flag.Bool("u", false, "ignored")
 )
 
-func catFile(w io.Writer, file string) error {
-	f, err := os.Open(file)
-	if err != nil {
-		return err
+func cat(reader io.Reader, writer io.Writer) error {
+	if _, err := io.Copy(writer, reader); err != nil {
+		return fmt.Errorf("error concatenating stdin to stdout: %v", err)
 	}
-	defer f.Close()
-
-	_, err = io.Copy(w, f)
-	return err
+	return nil
 }
 
-func cat(w io.Writer, files []string) error {
-	for _, name := range files {
-		if err := catFile(w, name); err != nil {
+func run(args []string, stdin io.Reader, stdout io.Writer) error {
+	if stdin == nil {
+		stdin = os.Stdin
+	}
+	if stdout == nil {
+		stdout = os.Stdout
+	}
+	if len(args) == 0 {
+		if err := cat(stdin, stdout); err != nil {
+			return fmt.Errorf("error concatenating stdin to stdout: %v", err)
+		}
+	}
+	for _, file := range args {
+		f, err := os.Open(file)
+		if err != nil {
 			return err
 		}
+		if err := cat(f, stdout); err != nil {
+			return fmt.Errorf("failed to concatenate file %s to given writer", f.Name())
+		}
+		f.Close()
 	}
 	return nil
 }
 
 func main() {
 	flag.Parse()
-
-	if flag.NArg() == 0 {
-		if _, err := io.Copy(os.Stdout, os.Stdin); err != nil {
-			log.Fatalf("error concatenating stdin to stdout: %v", err)
-		}
-	}
-
-	if err := cat(os.Stdout, flag.Args()); err != nil {
-		log.Fatalf("cat: %v", err)
+	if err := run(os.Args[1:], nil, nil); err != nil {
+		log.Fatalf("cat failed with: %v", err)
 	}
 }

cmds/core/cat/cat_test.go

@@ -50,12 +50,83 @@ func TestCat(t *testing.T) {
 	for i := range someData {
 		files = append(files, fmt.Sprintf("%v%d", filepath.Join(dir, "file"), i))
 	}
-
-	var b bytes.Buffer
-	if err := cat(&b, files); err != nil {
+	var out bytes.Buffer
+	if err := run(files, nil, &out); err != nil {
 		t.Fatal(err)
 	}
-	if !reflect.DeepEqual(b.Bytes(), someData) {
-		t.Fatalf("Reading files failed: got %v, want %v", b.Bytes(), someData)
+
+	if !reflect.DeepEqual(out.Bytes(), someData) {
+		t.Fatalf("Reading files failed: got %v, want %v", out.Bytes(), someData)
+	}
+}
+
+func TestCatPipe(t *testing.T) {
+	var inputbuf bytes.Buffer
+	teststring := "testdata"
+	fmt.Fprintf(&inputbuf, "%s", teststring)
+
+	var out bytes.Buffer
+
+	if err := cat(&inputbuf, &out); err != nil {
+		t.Error(err)
+	}
+	if out.String() != teststring {
+		t.Errorf("CatPipe: Want %q Got: %q", teststring, out.String())
+	}
+}
+
+func TestRunFiles(t *testing.T) {
+	var files []string
+	someData := []byte{'l', 2, 3, 4, 'd'}
+
+	dir, err := setup(t, someData)
+	if err != nil {
+		t.Fatalf("setup has failed, %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	for i := range someData {
+		files = append(files, fmt.Sprintf("%v%d", filepath.Join(dir, "file"), i))
+	}
+
+	var out bytes.Buffer
+	if err := run(files, nil, &out); err != nil {
+		t.Error(err)
+	}
+	if !reflect.DeepEqual(out.Bytes(), someData) {
+		t.Fatalf("Reading files failed: got %v, want %v", out.Bytes(), someData)
+	}
+}
+
+func TestRunFilesError(t *testing.T) {
+	var files []string
+	someData := []byte{'l', 2, 3, 4, 'd'}
+
+	dir, err := setup(t, someData)
+	if err != nil {
+		t.Fatalf("setup has failed, %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	for i := range someData {
+		files = append(files, fmt.Sprintf("%v%d", filepath.Join(dir, "file"), i))
+	}
+	filenotexist := "testdata/doesnotexist.txt"
+	files = append(files, filenotexist)
+	if err := run(files, nil, nil); err == nil {
+		t.Error("function run succeeded but should have failed")
+	}
+}
+
+func TestRunNoArgs(t *testing.T) {
+	var in, out bytes.Buffer
+	inputdata := "teststring"
+	fmt.Fprintf(&in, "%s", inputdata)
+	args := make([]string, 0)
+	if err := run(args, &in, &out); err != nil {
+		t.Error(err)
+	}
+	if out.String() != inputdata {
+		t.Errorf("Want: %q Got: %q", inputdata, out.String())
 	}
 }