test: Check created_at for prepareData to ensure user order (#6436)

* test: Check created_at for prepareData to ensure user order

* test: Consistent user ordering in dbfake

* import order

* Linting

coderd/database/dbfake/databasefake.go

@@ -2922,6 +2922,21 @@ func (q *fakeQuerier) InsertUser(_ context.Context, arg database.InsertUserParam
 		return database.User{}, err
 	}
 
+	// There is a common bug when using dbfake that 2 inserted users have the
+	// same created_at time. This causes user order to not be deterministic,
+	// which breaks some unit tests.
+	// To fix this, we make sure that the created_at time is always greater
+	// than the last user's created_at time.
+	allUsers, _ := q.GetUsers(context.Background(), database.GetUsersParams{})
+	if len(allUsers) > 0 {
+		lastUser := allUsers[len(allUsers)-1]
+		if arg.CreatedAt.Before(lastUser.CreatedAt) ||
+			arg.CreatedAt.Equal(lastUser.CreatedAt) {
+			// 1 ms is a good enough buffer.
+			arg.CreatedAt = lastUser.CreatedAt.Add(time.Millisecond)
+		}
+	}
+
 	q.mutex.Lock()
 	defer q.mutex.Unlock()
 

coderd/database/dbfake/databasefake_test.go

@@ -9,10 +9,11 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/coder/coder/coderd/database"
-
 	"github.com/coder/coder/coderd/database/dbfake"
+	"github.com/coder/coder/coderd/database/dbgen"
 )
 
 // test that transactions don't deadlock, and that we don't see intermediate state.
@@ -105,6 +106,29 @@ func TestExactMethods(t *testing.T) {
 	}
 }
 
+// TestUserOrder ensures that the fake database returns users in the order they
+// were created.
+func TestUserOrder(t *testing.T) {
+	t.Parallel()
+
+	db := dbfake.New()
+	now := database.Now()
+	count := 10
+	for i := 0; i < count; i++ {
+		dbgen.User(t, db, database.User{
+			Username:  fmt.Sprintf("user%d", i),
+			CreatedAt: now,
+		})
+	}
+
+	users, err := db.GetUsers(context.Background(), database.GetUsersParams{})
+	require.NoError(t, err)
+	require.Lenf(t, users, count, "expected %d users", count)
+	for i, user := range users {
+		require.Equal(t, fmt.Sprintf("user%d", i), user.Username)
+	}
+}
+
 func methods(rt reflect.Type) map[string]bool {
 	methods := make(map[string]bool)
 	for i := 0; i < rt.NumMethod(); i++ {