Implement Assert

constructor/worker/worker.go

@@ -66,6 +66,8 @@ func (w *Worker) invokeWorker(
 		return w.FindBalanceWorker(ctx, dbTx, input)
 	case job.RandomNumber:
 		return RandomNumberWorker(input)
+	case job.Assert:
+		return "", AssertWorker(input)
 	default:
 		return "", fmt.Errorf("%w: %s", ErrInvalidActionType, action)
 	}
@@ -615,3 +617,25 @@ func (w *Worker) FindBalanceWorker(
 	// and should just return unsatisfiable.
 	return "", ErrUnsatisfiable
 }
+
+// AssertWorker checks if an input is < 0.
+func AssertWorker(rawInput string) error {
+	// We unmarshal the input here to handle string
+	// unwrapping automatically.
+	var input string
+	err := job.UnmarshalInput([]byte(rawInput), &input)
+	if err != nil {
+		return fmt.Errorf("%w: %s", ErrInvalidInput, err.Error())
+	}
+
+	val, err := types.BigInt(input)
+	if err != nil {
+		return fmt.Errorf("%w: %s", ErrInvalidInput, err.Error())
+	}
+
+	if val.Sign() < 0 {
+		return fmt.Errorf("%w: %s < 0", ErrActionFailed, val.String())
+	}
+
+	return nil
+}

constructor/worker/worker_test.go

@@ -1032,6 +1032,10 @@ func TestJob_ComplicatedTransfer(t *testing.T) {
 				Input:      `{"minimum":"10", "maximum":"100"}`,
 				OutputPath: "rand_number",
 			},
+			{
+				Type:  job.Assert,
+				Input: `{{rand_number}}`,
+			},
 			{
 				Type:  job.PrintMessage,
 				Input: `{"random_number": {{rand_number}}}`,
@@ -1195,6 +1199,32 @@ func TestJob_Failures(t *testing.T) {
 			expectedErr: ErrInvalidActionType,
 			helper:      &mocks.Helper{},
 		},
+		"assertion invalid input": {
+			scenario: &job.Scenario{
+				Name: "create_address",
+				Actions: []*job.Action{
+					{
+						Type:  "assert",
+						Input: `"hello"`,
+					},
+				},
+			},
+			expectedErr: ErrInvalidInput,
+			helper:      &mocks.Helper{},
+		},
+		"failed assertion": {
+			scenario: &job.Scenario{
+				Name: "create_address",
+				Actions: []*job.Action{
+					{
+						Type:  "assert",
+						Input: `"-1"`,
+					},
+				},
+			},
+			expectedErr: ErrActionFailed,
+			helper:      &mocks.Helper{},
+		},
 		"invalid json": {
 			scenario: &job.Scenario{
 				Name: "create_address",