test: add deezer crypto and filename tests

internal/deezer/ecb_test.go

@@ -0,0 +1,72 @@
+package deezer
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestZeroPad(t *testing.T) {
+	tests := []struct {
+		length int
+		want   int
+	}{
+		{0, 0},
+		{1, 16},
+		{15, 16},
+		{16, 16},
+		{17, 32},
+	}
+
+	for _, tt := range tests {
+		padded := zeroPad(make([]byte, tt.length))
+		if len(padded) != tt.want {
+			t.Errorf("zeroPad(len %d) = len %d, want %d", tt.length, len(padded), tt.want)
+		}
+	}
+}
+
+func TestZeroPadPreservesData(t *testing.T) {
+	data := []byte("secret")
+	padded := zeroPad(data)
+
+	if !bytes.Equal(padded[:len(data)], data) {
+		t.Errorf("zeroPad changed data: got %q", padded[:len(data)])
+	}
+	for _, b := range padded[len(data):] {
+		if b != 0 {
+			t.Errorf("padding is not zero: %v", padded)
+		}
+	}
+}
+
+func TestECBRoundTrip(t *testing.T) {
+	key := []byte("0123456789abcdef")
+	plaintext := zeroPad([]byte("some secret data"))
+
+	encrypted, err := ecbEncrypt(key, plaintext)
+	if err != nil {
+		t.Fatalf("ecbEncrypt: %v", err)
+	}
+	if bytes.Equal(encrypted, plaintext) {
+		t.Fatal("encrypted data equals plaintext")
+	}
+
+	decrypted, err := ecbDecrypt(key, encrypted)
+	if err != nil {
+		t.Fatalf("ecbDecrypt: %v", err)
+	}
+	if !bytes.Equal(decrypted, plaintext) {
+		t.Errorf("round trip mismatch: got %q, want %q", decrypted, plaintext)
+	}
+}
+
+func TestECBRejectsPartialBlock(t *testing.T) {
+	key := []byte("0123456789abcdef")
+
+	if _, err := ecbEncrypt(key, make([]byte, 15)); err == nil {
+		t.Error("expected error for data not a multiple of the block size")
+	}
+	if _, err := ecbDecrypt(key, make([]byte, 17)); err == nil {
+		t.Error("expected error for data not a multiple of the block size")
+	}
+}