test: mongodb custom built-ins unit tests (#436)

* test: mongodb utilities test refactor

* test: mongodb custom builtins tests

Author: fredmaggiowski

custom_builtins/mongo.go

@@ -38,39 +38,41 @@ var MongoFindOne = rego.Function2(
 		Name: MongoFindOneDecl.Name,
 		Decl: MongoFindOneDecl.Decl,
 	},
-	func(ctx rego.BuiltinContext, collectionNameTerm, queryTerm *ast.Term) (*ast.Term, error) {
-		mongoClient, err := GetMongoClientFromContext(ctx.Context)
-		if err != nil {
-			return nil, err
-		}
-		if mongoClient == nil {
-			return nil, fmt.Errorf("mongo client not set")
-		}
-
-		var collectionName string
-		if err := ast.As(collectionNameTerm.Value, &collectionName); err != nil {
-			return nil, err
-		}
-
-		query := make(map[string]interface{})
-		if err := ast.As(queryTerm.Value, &query); err != nil {
-			return nil, err
-		}
-
-		result, err := mongoClient.FindOne(ctx.Context, collectionName, query)
-		if err != nil {
-			return nil, err
-		}
-
-		t, err := ast.InterfaceToValue(result)
-		if err != nil {
-			return nil, err
-		}
-
-		return ast.NewTerm(t), nil
-	},
+	mongoFindOneDef,
 )
 
+func mongoFindOneDef(ctx rego.BuiltinContext, collectionNameTerm, queryTerm *ast.Term) (*ast.Term, error) {
+	mongoClient, err := GetMongoClientFromContext(ctx.Context)
+	if err != nil {
+		return nil, err
+	}
+	if mongoClient == nil {
+		return nil, fmt.Errorf("mongo client not set")
+	}
+
+	var collectionName string
+	if err := ast.As(collectionNameTerm.Value, &collectionName); err != nil {
+		return nil, err
+	}
+
+	query := make(map[string]interface{})
+	if err := ast.As(queryTerm.Value, &query); err != nil {
+		return nil, err
+	}
+
+	result, err := mongoClient.FindOne(ctx.Context, collectionName, query)
+	if err != nil {
+		return nil, err
+	}
+
+	t, err := ast.InterfaceToValue(result)
+	if err != nil {
+		return nil, err
+	}
+
+	return ast.NewTerm(t), nil
+}
+
 var MongoFindManyDecl = &ast.Builtin{
 	Name: "find_many",
 	Decl: types.NewFunction(

custom_builtins/mongo_test.go

@@ -0,0 +1,102 @@
+// Copyright 2025 Mia srl
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package custom_builtins
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/open-policy-agent/opa/ast"
+	"github.com/open-policy-agent/opa/rego"
+	"github.com/rond-authz/rond/custom_builtins/mocks"
+	"github.com/stretchr/testify/require"
+)
+
+func prepareContext(t *testing.T, mongoClientMock *mocks.MongoClientMock) rego.BuiltinContext {
+	t.Helper()
+
+	ctx := context.Background()
+
+	if mongoClientMock != nil {
+		ctx = WithMongoClient(ctx, mongoClientMock)
+	}
+
+	return rego.BuiltinContext{
+		Context: ctx,
+	}
+}
+
+func TestMongoFindOneDefinition(t *testing.T) {
+	defaultMock := &mocks.MongoClientMock{}
+
+	t.Run("returns error if mongo client is not set", func(t *testing.T) {
+		_, err := mongoFindOneDef(
+			prepareContext(t, nil),
+			nil,
+			nil,
+		)
+		require.ErrorContains(t, err, "mongo client not set")
+	})
+
+	t.Run("returns error if mongo client in context is not valid", func(t *testing.T) {
+		_, err := mongoFindOneDef(
+			rego.BuiltinContext{
+				Context: context.WithValue(context.Background(), mongoClientCustomBuiltinContextKey{}, "not a valid client"),
+			},
+			nil,
+			nil,
+		)
+		require.ErrorContains(t, err, "no MongoDB client found in context")
+	})
+
+	t.Run("returns error if collection name is not a string", func(t *testing.T) {
+		_, err := mongoFindOneDef(
+			prepareContext(t, defaultMock),
+			ast.BooleanTerm(false),
+			nil,
+		)
+		require.ErrorContains(t, err, "cannot unmarshal bool")
+	})
+
+	t.Run("returns error if query is not an object", func(t *testing.T) {
+		_, err := mongoFindOneDef(prepareContext(
+			t,
+			defaultMock),
+			ast.StringTerm("coll"),
+			ast.BooleanTerm(false),
+		)
+		require.ErrorContains(t, err, "cannot unmarshal bool")
+	})
+
+	t.Run("returns error if FindOne returns an error", func(t *testing.T) {
+		assertionInvoked := false
+		mock := &mocks.MongoClientMock{
+			FindOneError: errors.New("some error"),
+			FindOneExpectation: func(collectionName string, query interface{}) {
+				assertionInvoked = true
+				require.Equal(t, "coll", collectionName)
+				require.Equal(t, map[string]interface{}{}, query)
+			},
+		}
+		_, err := mongoFindOneDef(
+			prepareContext(t, mock),
+			ast.StringTerm("coll"),
+			ast.MustParseTerm("{}"),
+		)
+		require.ErrorContains(t, err, "some error")
+		require.True(t, assertionInvoked)
+	})
+}