Add fuzz test for rego evaluator

internal/engine/eval/rego/fuzz_test.go

@@ -0,0 +1,51 @@
+// Copyright 2024 Stacklok, Inc.
+//
+// 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 rego
+
+import (
+	"context"
+	"testing"
+
+	engif "github.com/stacklok/minder/internal/engine/interfaces"
+	minderv1 "github.com/stacklok/minder/pkg/api/protobuf/go/minder/v1"
+)
+
+// FuzzRegoEval tests for unexpected behavior in e.Eval().
+// The test does not validate the return values from e.Eval().
+func FuzzRegoEval(f *testing.F) {
+	f.Fuzz(func(_ *testing.T, policy, data string) {
+		e, err := NewRegoEvaluator(
+			&minderv1.RuleType_Definition_Eval_Rego{
+				Type: ConstraintsEvaluationType.String(),
+				Def:  policy,
+			},
+		)
+		if err != nil {
+			return
+		}
+
+		emptyPol := map[string]any{}
+
+		// Call the main target of this test. Ignore the return values;
+		// The fuzzer tests for unexpected behavior, so it is not
+		// important what e.Eval() returns.
+		//nolint:gosec // Ignore the return values from e.Eval()
+		e.Eval(context.Background(), emptyPol, &engif.Result{
+			Object: map[string]any{
+				"data": data,
+			},
+		})
+	})
+}