test: add integration test

.gitignore

@@ -23,4 +23,5 @@ dockerfilegraph
 # dockerfilegraph
 Dockerfile.*
 !/Dockerfile.alpine
+!Dockerfile.golden.dot
 !examples/dockerfiles/Dockerfile.large

internal/cmd/integration_test.go

@@ -0,0 +1,106 @@
+package cmd_test
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestIntegrationCLIGeneratesOutputFile(t *testing.T) {
+	// Find the project root directory
+	_, thisFile, _, _ := runtime.Caller(0)
+	projectRoot := filepath.Clean(filepath.Join(filepath.Dir(thisFile), "../.."))
+
+	// Build the Linux binary before building the Docker image
+	makeCmd := exec.Command("make", "build-linux")
+	makeCmd.Dir = projectRoot
+	makeOut, err := makeCmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("make build-linux failed: %v\nOutput:\n%s", err, string(makeOut))
+	}
+	binPath := filepath.Join(projectRoot, "dockerfilegraph")
+	defer func() {
+		if err := os.Remove(binPath); err != nil && !os.IsNotExist(err) {
+			t.Errorf("failed to remove built binary %s: %v", binPath, err)
+		}
+	}()
+
+	// Build the Docker image from the project root
+	buildCmd := exec.Command("docker", "build", "-t", "dockerfilegraph-test", "-f", "Dockerfile", ".")
+	buildCmd.Dir = projectRoot
+	buildOut, err := buildCmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("docker build failed: %v\nOutput:\n%s", err, string(buildOut))
+	}
+
+	// Prepare temp dir for output
+	tempDir := t.TempDir()
+	// Copy example Dockerfile to temp dir
+	dockerfileSrc := filepath.Join(projectRoot, "examples", "dockerfiles", "Dockerfile")
+	dockerfileDst := filepath.Join(tempDir, "Dockerfile")
+	content, err := os.ReadFile(dockerfileSrc)
+	if err != nil {
+		t.Fatalf("failed to read example Dockerfile from %s: %v", dockerfileSrc, err)
+	}
+	if err := os.WriteFile(dockerfileDst, content, 0644); err != nil {
+		t.Fatalf("failed to write Dockerfile to temp dir %s: %v", dockerfileDst, err)
+	}
+
+	// Run the CLI in Docker to generate Dockerfile.dot
+	dockerCmd := exec.Command(
+		"docker", "run", "--rm",
+		"-u", fmt.Sprintf("%d:%d", os.Getuid(), os.Getgid()),
+		"-v", tempDir+":/data",
+		"-w", "/data",
+		"dockerfilegraph-test",
+		"--filename", "Dockerfile", "--output", "dot",
+	)
+	dockerOut, err := dockerCmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("docker run CLI failed: %v\nOutput:\n%s", err, string(dockerOut))
+	}
+
+	// Read the DOT file generated by the CLI
+	dotFile := filepath.Join(tempDir, "Dockerfile.dot")
+	outputBytes, err := os.ReadFile(dotFile)
+	if err != nil {
+		t.Fatalf("failed to read generated dot file %s: %v", dotFile, err)
+	}
+
+	checkGoldenFile(t, outputBytes)
+}
+
+func checkGoldenFile(t *testing.T, dotBytes []byte) {
+	_, thisFile, _, _ := runtime.Caller(0)
+	goldenDir := filepath.Join(filepath.Dir(thisFile), "testdata")
+	goldenFile := filepath.Join(goldenDir, "Dockerfile.golden.dot")
+
+	if _, err := os.Stat(goldenFile); os.IsNotExist(err) {
+		if err := os.MkdirAll(goldenDir, 0755); err != nil {
+			t.Fatalf("failed to create testdata dir: %v", err)
+		}
+		if err := os.WriteFile(goldenFile, dotBytes, 0644); err != nil {
+			t.Fatalf("failed to write golden file: %v", err)
+		}
+		t.Logf("golden file did not exist, created: %s", goldenFile)
+	} else {
+		goldenBytes, err := os.ReadFile(goldenFile)
+		if err != nil {
+			t.Fatalf("failed to read golden file: %v", err)
+		}
+		diff := cmp.Diff(string(goldenBytes), string(dotBytes))
+		if diff != "" {
+			t.Errorf(
+				"output DOT does not match golden file.\n"+
+					"To update, delete %s and re-run the test.\n"+
+					"Diff (-want +got):\n%s",
+				goldenFile, diff,
+			)
+		}
+	}
+}

internal/cmd/testdata/Dockerfile.golden.dot

@@ -0,0 +1,72 @@
+digraph G {
+	graph [bb="0,0,543,252",
+		compound=true,
+		nodesep=1.00,
+		rankdir=LR,
+		ranksep=0.50
+	];
+	node [label="\N"];
+	external_image_0	[color=grey20,
+		fontcolor=grey20,
+		height=0.5,
+		label="ubuntu:l...887c2c7ac",
+		pos="86,234",
+		shape=box,
+		style="dashed,rounded",
+		width=2.3056];
+	stage_0	[height=0.5,
+		label=ubuntu,
+		pos="285.5,234",
+		shape=box,
+		style=rounded,
+		width=2];
+	external_image_0 -> stage_0	[pos="e,213.41,234 169.04,234 180.32,234 191.9,234 203.17,234"];
+	stage_2	[fillcolor=grey90,
+		height=0.5,
+		label=release,
+		pos="471,126",
+		shape=box,
+		style="filled,rounded",
+		width=2];
+	stage_0 -> stage_2	[arrowhead=empty,
+		pos="e,439.19,144.14 317.21,215.92 348.31,197.62 396.52,169.25 430.45,149.28",
+		style=dashed];
+	external_image_1	[color=grey20,
+		fontcolor=grey20,
+		height=0.5,
+		label="golang:1...b738433da",
+		pos="86,126",
+		shape=box,
+		style="dashed,rounded",
+		width=2.3889];
+	stage_1	[height=0.5,
+		label="build-tool-depend...",
+		pos="285.5,126",
+		shape=box,
+		style=rounded,
+		width=2.1528];
+	external_image_1 -> stage_1	[pos="e,207.99,126 172.19,126 180.65,126 189.25,126 197.73,126"];
+	stage_1 -> stage_2	[arrowhead=empty,
+		pos="e,398.82,126 363.26,126 371.64,126 380.19,126 388.62,126",
+		style=dashed];
+	external_image_2	[color=grey20,
+		fontcolor=grey20,
+		height=0.5,
+		label=buildcache,
+		pos="86,18",
+		shape=box,
+		style="dashed,rounded",
+		width=2];
+	external_image_2 -> stage_1	[arrowhead=ediamond,
+		pos="e,251.34,107.86 120.06,36.077 153.1,54.144 204.09,82.03 240.53,101.96",
+		style=dotted];
+	external_image_3	[color=grey20,
+		fontcolor=grey20,
+		height=0.5,
+		label=scratch,
+		pos="285.5,18",
+		shape=box,
+		style="dashed,rounded",
+		width=2];
+	external_image_3 -> stage_2	[pos="e,439.19,107.86 317.21,36.077 348.31,54.378 396.52,82.753 430.45,102.72"];
+}