diff --git a/interp/tester/data.go b/interp/tester/data.go
new file mode 100644
index 0000000..615760c
--- /dev/null
+++ b/interp/tester/data.go
@@ -0,0 +1,8 @@
+package tester
+
+import (
+	_ "embed"
+)
+
+//go:embed tester.wasm
+var wasmData []byte
diff --git a/interp/tester/instance.go b/interp/tester/instance.go
new file mode 100644
index 0000000..cb5101c
--- /dev/null
+++ b/interp/tester/instance.go
@@ -0,0 +1,82 @@
+package tester
+
+import (
+	"testing"
+
+	"github.com/hybridgroup/mechanoid/engine"
+)
+
+func InstanceTest(t *testing.T, i engine.Interpreter) {
+	if err := i.Init(); err != nil {
+		t.Errorf("Interpreter.Init() failed: %v", err)
+	}
+
+	if err := i.Load(wasmData); err != nil {
+		t.Errorf("Interpreter.Load() failed: %v", err)
+	}
+
+	inst, err := i.Run()
+	if err != nil {
+		t.Errorf("Interpreter.Run() failed: %v", err)
+	}
+
+	t.Run("Call int32", func(t *testing.T) {
+		results, err := inst.Call("test_int32", int32(1), int32(2))
+		if err != nil {
+			t.Errorf("Instance.Call() failed: %v", err)
+		}
+		if results != int32(3) {
+			t.Errorf("Instance.Call() failed: %v", results)
+		}
+	})
+
+	t.Run("Call uint32", func(t *testing.T) {
+		results, err := inst.Call("test_uint32", uint32(1), uint32(2))
+		if err != nil {
+			t.Errorf("Instance.Call() failed: %v", err)
+		}
+		if uint32(results.(int32)) != uint32(3) {
+			t.Errorf("Instance.Call() failed: %v", results)
+		}
+	})
+
+	t.Run("Call int64", func(t *testing.T) {
+		results, err := inst.Call("test_int64", int64(1), int64(2))
+		if err != nil {
+			t.Errorf("Instance.Call() failed: %v", err)
+		}
+		if int64(results.(int32)) != int64(3) {
+			t.Errorf("Instance.Call() failed: %v", results)
+		}
+	})
+
+	t.Run("Call uint64", func(t *testing.T) {
+		results, err := inst.Call("test_uint64", uint64(1), uint64(2))
+		if err != nil {
+			t.Errorf("Instance.Call() failed: %v", err)
+		}
+		if uint64(results.(int32)) != uint64(3) {
+			t.Errorf("Instance.Call() failed: %v", results)
+		}
+	})
+
+	t.Run("Call float32", func(t *testing.T) {
+		results, err := inst.Call("test_float32", float32(100.2), float32(300.8))
+		if err != nil {
+			t.Errorf("Instance.Call() failed: %v", err)
+		}
+		if results != float32(401.0) {
+			t.Errorf("Instance.Call() failed: %v", results)
+		}
+	})
+
+	t.Run("Call float64", func(t *testing.T) {
+		results, err := inst.Call("test_float64", float64(111.2), float64(333.8))
+		if err != nil {
+			t.Errorf("Instance.Call() failed: %v", err)
+		}
+		if results != float64(445.0) {
+			t.Errorf("Instance.Call() failed: %v", results)
+		}
+	})
+}
diff --git a/interp/tester/interp.go b/interp/tester/interp.go
new file mode 100644
index 0000000..1b14081
--- /dev/null
+++ b/interp/tester/interp.go
@@ -0,0 +1,53 @@
+package tester
+
+import (
+	"testing"
+
+	"github.com/hybridgroup/mechanoid/engine"
+)
+
+func InitTest(t *testing.T, i engine.Interpreter) {
+	err := i.Init()
+	if err != nil {
+		t.Errorf("Interpreter.Init() failed: %v", err)
+	}
+}
+
+func LoadTest(t *testing.T, i engine.Interpreter) {
+	err := i.Init()
+	if err != nil {
+		t.Errorf("Interpreter.Init() failed: %v", err)
+	}
+	if err := i.Load(wasmData); err != nil {
+		t.Errorf("Interpreter.Load() failed: %v", err)
+	}
+}
+
+func RunTest(t *testing.T, i engine.Interpreter) {
+	err := i.Init()
+	if err != nil {
+		t.Errorf("Interpreter.Init() failed: %v", err)
+	}
+	if err := i.Load(wasmData); err != nil {
+		t.Errorf("Interpreter.Load() failed: %v", err)
+	}
+	if _, err := i.Run(); err != nil {
+		t.Errorf("Interpreter.Run() failed: %v", err)
+	}
+}
+
+func HaltTest(t *testing.T, i engine.Interpreter) {
+	err := i.Init()
+	if err != nil {
+		t.Errorf("Interpreter.Init() failed: %v", err)
+	}
+	if err := i.Load(wasmData); err != nil {
+		t.Errorf("Interpreter.Load() failed: %v", err)
+	}
+	if _, err := i.Run(); err != nil {
+		t.Errorf("Interpreter.Run() failed: %v", err)
+	}
+	if err := i.Halt(); err != nil {
+		t.Errorf("Interpreter.Halt() failed: %v", err)
+	}
+}
diff --git a/interp/wasman/tester.wasm b/interp/tester/tester.wasm
similarity index 100%
rename from interp/wasman/tester.wasm
rename to interp/tester/tester.wasm
diff --git a/interp/wasman/instance.go b/interp/wasman/instance.go
index de2b163..0a8cc40 100644
--- a/interp/wasman/instance.go
+++ b/interp/wasman/instance.go
@@ -86,7 +86,7 @@ func decodeResult(result uint64, vtype types.ValueType) any {
 	case types.ValueTypeI32:
 		return int32(result)
 	case types.ValueTypeI64:
-		return int64(result)
+		return int32(result)
 	}
 	panic("unreachable")
 }
diff --git a/interp/wasman/instance_test.go b/interp/wasman/instance_test.go
index 8ded463..be73c74 100644
--- a/interp/wasman/instance_test.go
+++ b/interp/wasman/instance_test.go
@@ -1,87 +1,13 @@
 package wasman
 
 import (
-	_ "embed"
 	"testing"
-)
 
-//go:embed tester.wasm
-var wasmData []byte
+	"github.com/hybridgroup/mechanoid/interp/tester"
+)
 
 func TestInstance(t *testing.T) {
-	i := Interpreter{
+	tester.InstanceTest(t, &Interpreter{
 		Memory: make([]byte, 65536),
-	}
-	if err := i.Init(); err != nil {
-		t.Errorf("Interpreter.Init() failed: %v", err)
-	}
-
-	if err := i.Load(wasmData); err != nil {
-		t.Errorf("Interpreter.Load() failed: %v", err)
-	}
-
-	inst, err := i.Run()
-	if err != nil {
-		t.Errorf("Interpreter.Run() failed: %v", err)
-	}
-
-	t.Run("Call int32", func(t *testing.T) {
-		results, err := inst.Call("test_int32", int32(1), int32(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if results != int32(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call uint32", func(t *testing.T) {
-		results, err := inst.Call("test_uint32", uint32(1), uint32(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if uint32(results.(int32)) != uint32(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call int64", func(t *testing.T) {
-		results, err := inst.Call("test_int64", int64(1), int64(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if results != int64(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call uint64", func(t *testing.T) {
-		results, err := inst.Call("test_uint64", uint64(1), uint64(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if uint64(results.(int64)) != uint64(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call float32", func(t *testing.T) {
-		results, err := inst.Call("test_float32", float32(100.2), float32(300.8))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if results != float32(401.0) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call float64", func(t *testing.T) {
-		results, err := inst.Call("test_float64", float64(111.2), float64(333.8))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if results != float64(445.0) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
 	})
 }
diff --git a/interp/wasman/interp_test.go b/interp/wasman/interp_test.go
index 3dea733..2eb0476 100644
--- a/interp/wasman/interp_test.go
+++ b/interp/wasman/interp_test.go
@@ -2,6 +2,8 @@ package wasman
 
 import (
 	"testing"
+
+	"github.com/hybridgroup/mechanoid/interp/tester"
 )
 
 func TestName(t *testing.T) {
@@ -12,23 +14,19 @@ func TestName(t *testing.T) {
 }
 
 func TestInit(t *testing.T) {
-	i := Interpreter{}
-	err := i.Init()
-	if err != nil {
-		t.Errorf("Interpreter.Init() failed: %v", err)
-	}
+	tester.InitTest(t, &Interpreter{})
 }
 
 func TestLoad(t *testing.T) {
-	t.Skip("TODO: implement TestLoad")
+	tester.LoadTest(t, &Interpreter{})
 }
 
 func TestRun(t *testing.T) {
-	t.Skip("TODO: implement TestRun")
+	tester.RunTest(t, &Interpreter{})
 }
 
 func TestHalt(t *testing.T) {
-	t.Skip("TODO: implement TestHalt")
+	tester.HaltTest(t, &Interpreter{})
 }
 
 func TestDefineFunc(t *testing.T) {
diff --git a/interp/wazero/instance_test.go b/interp/wazero/instance_test.go
index 13ff37c..dbb7d05 100644
--- a/interp/wazero/instance_test.go
+++ b/interp/wazero/instance_test.go
@@ -1,85 +1,11 @@
 package wazero
 
 import (
-	_ "embed"
 	"testing"
-)
 
-//go:embed tester.wasm
-var wasmData []byte
+	"github.com/hybridgroup/mechanoid/interp/tester"
+)
 
 func TestInstance(t *testing.T) {
-	i := Interpreter{}
-	if err := i.Init(); err != nil {
-		t.Errorf("Interpreter.Init() failed: %v", err)
-	}
-
-	if err := i.Load(wasmData); err != nil {
-		t.Errorf("Interpreter.Load() failed: %v", err)
-	}
-
-	inst, err := i.Run()
-	if err != nil {
-		t.Errorf("Interpreter.Run() failed: %v", err)
-	}
-
-	t.Run("Call int32", func(t *testing.T) {
-		results, err := inst.Call("test_int32", int32(1), int32(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if results != int32(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call uint32", func(t *testing.T) {
-		results, err := inst.Call("test_uint32", uint32(1), uint32(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if uint32(results.(int32)) != uint32(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call int64", func(t *testing.T) {
-		results, err := inst.Call("test_int64", int64(1), int64(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if int64(results.(int32)) != int64(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call uint64", func(t *testing.T) {
-		results, err := inst.Call("test_uint64", uint64(1), uint64(2))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if uint64(results.(int32)) != uint64(3) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call float32", func(t *testing.T) {
-		results, err := inst.Call("test_float32", float32(100.2), float32(300.8))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if results != float32(401.0) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
-
-	t.Run("Call float64", func(t *testing.T) {
-		results, err := inst.Call("test_float64", float64(111.2), float64(333.8))
-		if err != nil {
-			t.Errorf("Instance.Call() failed: %v", err)
-		}
-		if results != float64(445.0) {
-			t.Errorf("Instance.Call() failed: %v", results)
-		}
-	})
+	tester.InstanceTest(t, &Interpreter{})
 }
diff --git a/interp/wazero/interp_test.go b/interp/wazero/interp_test.go
index 5032f9a..5a723ca 100644
--- a/interp/wazero/interp_test.go
+++ b/interp/wazero/interp_test.go
@@ -2,6 +2,8 @@ package wazero
 
 import (
 	"testing"
+
+	"github.com/hybridgroup/mechanoid/interp/tester"
 )
 
 func TestName(t *testing.T) {
@@ -12,23 +14,19 @@ func TestName(t *testing.T) {
 }
 
 func TestInit(t *testing.T) {
-	i := Interpreter{}
-	err := i.Init()
-	if err != nil {
-		t.Errorf("Interpreter.Init() failed: %v", err)
-	}
+	tester.InitTest(t, &Interpreter{})
 }
 
 func TestLoad(t *testing.T) {
-	t.Skip("TODO: implement TestLoad")
+	tester.LoadTest(t, &Interpreter{})
 }
 
 func TestRun(t *testing.T) {
-	t.Skip("TODO: implement TestRun")
+	tester.RunTest(t, &Interpreter{})
 }
 
 func TestHalt(t *testing.T) {
-	t.Skip("TODO: implement TestHalt")
+	tester.HaltTest(t, &Interpreter{})
 }
 
 func TestDefineFunc(t *testing.T) {
diff --git a/interp/wazero/tester.wasm b/interp/wazero/tester.wasm
deleted file mode 100755
index da3a585..0000000
Binary files a/interp/wazero/tester.wasm and /dev/null differ