1 files changed, 58 insertions, 1 deletions
diff --git a/evaluator/evaluator_test.go b/evaluator/evaluator_test.go
index ca7738f..6553f55 100644
--- a/evaluator/evaluator_test.go
+++ b/evaluator/evaluator_test.go
@@ -5,7 +5,7 @@ import (
 	"mana/object"
 	"mana/parser"
 
-	"testing"
+  "testing"
 )
 
 func TestEvalIntegerExpression(t *testing.T) {
@@ -137,6 +137,63 @@ func TestReturnStatements(t *testing.T) {
 	}
 }
 
+func TestErrorhandling(t *testing.T) {
+  tests := [] struct {
+    input string
+    expectedMessage string
+  } {
+    {
+      "5 + true;",
+      "type mismatch: INTEGER + BOOLEAN",
+    },
+    {
+      "5 + true; 5;",
+      "type mismatch: INTEGER + BOOLEAN",
+    },
+    {
+      "-true",
+      "unknown operator: -BOOLEAN",
+    },
+    {
+      "true + false;",
+      "unknown operator: BOOLEAN + BOOLEAN",
+    },
+    {
+      "5; true + false; 5",
+      "unknown operator: BOOLEAN + BOOLEAN",
+    },
+    {
+      "if (10 > 1) { true + false; }",
+      "unknown operator: BOOLEAN + BOOLEAN",
+    },
+    {
+      `
+      if (10 > 1) {
+        if (10 > 1) {
+          return true + false;
+        }
+        return 1;
+      }
+      `,
+      "unknown operator: BOOLEAN + BOOLEAN",
+    },
+  }
+
+  for _, tt := range tests {
+    evaluated := testEval(tt.input)
+
+    errObj, ok := evaluated.(*object.Error)
+    if !ok {
+      t.Errorf("no error object returned. got=%T(%+v)", evaluated, evaluated)
+      continue
+    }
+
+    if errObj.Message != tt.expectedMessage {
+      t.Errorf("wrong error message. expected=%q, got=%q", tt.expectedMessage, errObj.Message)
+    }
+  }
+}
+
 func testEval(input string) object.Object {
 	l := lexer.New(input)
 	p := parser.New(l)