Add test for the wellknownfilewriter

Author: Joshua Krstic

launcher/container_runner_test.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path"
 	"strconv"
 	"testing"
 	"time"
@@ -651,6 +652,26 @@ func TestPullImageWithRetries(t *testing.T) {
 	}
 }
 
+func TestWellKnownFileLocationWriter(t *testing.T) {
+	if err := os.MkdirAll(launcherfile.HostTmpPath, 0755); err != nil {
+		t.Fatalf("Error creating host token path directory: %v", err)
+	}
+
+	fw := &wellKnownFileLocationWriter{}
+	testData := []byte("testing")
+	fw.Write(testData)
+
+	filepath := path.Join(launcherfile.HostTmpPath, launcherfile.AttestationVerifierTokenFilename)
+	data, err := os.ReadFile(filepath)
+	if err != nil {
+		t.Fatalf("Failed to read from %s: %v", filepath, err)
+	}
+
+	if !bytes.Equal(data, testData) {
+		t.Errorf("Initial token written to file does not match expected token: got %v, want %v", data, expectedToken)
+	}
+}
+
 // This ensures fakeContainer implements containerd.Container interface.
 var _ containerd.Container = &fakeContainer{}