client/v3/watch_test.go: test fmt metadata print

Signed-off-by: Mohamed Awnallah <[email protected]>

client/v3/watch_test.go

@@ -15,9 +15,11 @@
 package clientv3
 
 import (
+	"context"
 	"testing"
 
 	"go.etcd.io/etcd/api/v3/mvccpb"
+	"google.golang.org/grpc/metadata"
 )
 
 func TestEvent(t *testing.T) {
@@ -53,3 +55,53 @@ func TestEvent(t *testing.T) {
 		}
 	}
 }
+
+// TestStreamKeyFromCtx tests the streamKeyFromCtx function to ensure it correctly
+// formats metadata as a map[string][]string when extracting metadata from the context.
+//
+// The fmt package in Go guarantees that maps are printed in a consistent order,
+// sorted by the keys. This test verifies that the streamKeyFromCtx function
+// produces the expected formatted string representation of metadata maps when called with
+// various context scenarios.
+func TestStreamKeyFromCtx(t *testing.T) {
+	tests := []struct {
+		md       metadata.MD
+		expected string
+	}{
+		{
+			md: metadata.MD{
+				"key1": []string{"value1"},
+				"key2": []string{"value2a", "value2b"},
+			},
+			expected: "map[key1:[value1] key2:[value2a value2b]]",
+		},
+		{
+			md:       metadata.MD{},
+			expected: "map[]",
+		},
+		{
+			md: metadata.MD{
+				"key1": []string{"value1", "value1a"},
+			},
+			expected: "map[key1:[value1 value1a]]",
+		},
+	}
+
+	// Iterate through each test case and verify the function's output matches
+	// the expected result.
+	for i, tt := range tests {
+		ctx := metadata.NewOutgoingContext(context.Background(), tt.md)
+		actual := streamKeyFromCtx(ctx)
+		if actual != tt.expected {
+			t.Errorf("#%d: streamKeyFromCtx() = %v, want %v", i, actual, tt.expected)
+		}
+	}
+
+	// Test with no metadata in context to ensure it returns an empty string.
+	ctx := context.Background()
+	expected := ""
+	actual := streamKeyFromCtx(ctx)
+	if actual != expected {
+		t.Errorf("streamKeyFromCtx() = %v, want %v", actual, expected)
+	}
+}