#36: Add tests TestDB_WhereNotExists, Fix len for First

advanced.go

@@ -12,7 +12,10 @@ func (r *DB) First() (map[string]interface{}, error) {
 		return nil, err
 	}
 
-	return res[0], nil
+	if len(res) > 0 {
+		return res[0], nil
+	}
+	return nil, fmt.Errorf("no records were produced by query: %s", r.Builder.buildSelect())
 }
 
 // Value gets the value of column in first query resulting row

builder_test.go

@@ -352,10 +352,22 @@ func TestDB_WhereExists(t *testing.T) {
 		db.Table(UsersTable).Select("name").Where("points", ">=", int64(12345)),
 	).First()
 	assert.NoError(t, er)
+	assert.Equal(t, TestUserName, res["name"])
 
-	if res["name"] != TestUserName {
-		t.Fatalf("want %s, got: %s", TestUserName, res["name"])
-	}
+	db.Truncate(UsersTable)
+}
+
+func TestDB_WhereNotExists(t *testing.T) {
+	db.Truncate(UsersTable)
+
+	err := db.Table(UsersTable).InsertBatch(batchUsers)
+	assert.NoError(t, err)
+
+	res, er := db.Table(UsersTable).Select("name").WhereNotExists(
+		db.Table(UsersTable).Select("name").Where("points", ">=", int64(12345)),
+	).First()
+	assert.NoError(t, er)
+	assert.Equal(t, TestUserName, res["name"])
 
 	db.Truncate(UsersTable)
 }