diff --git a/src/types/Function.go b/src/types/Function.go
index 855e66b..7e19aac 100644
--- a/src/types/Function.go
+++ b/src/types/Function.go
@@ -33,7 +33,7 @@ func (f *Function) Name() string {
 		builder.WriteString(output.Name())
 
 		if i != len(f.Output)-1 {
-			builder.WriteString(",")
+			builder.WriteString(", ")
 		}
 	}
 
diff --git a/src/types/Function_test.go b/src/types/Function_test.go
new file mode 100644
index 0000000..dc6db48
--- /dev/null
+++ b/src/types/Function_test.go
@@ -0,0 +1,26 @@
+package types_test
+
+import (
+	"testing"
+
+	"git.urbach.dev/cli/q/src/types"
+	"git.urbach.dev/go/assert"
+)
+
+func TestFunction(t *testing.T) {
+	f := &types.Function{}
+	assert.Equal(t, f.Name(), "()")
+	assert.Equal(t, f.Size(), 8)
+
+	f.Input = append(f.Input, types.Int64)
+	assert.Equal(t, f.Name(), "(int64)")
+
+	f.Input = append(f.Input, types.Int64)
+	assert.Equal(t, f.Name(), "(int64, int64)")
+
+	f.Output = append(f.Output, types.Int64)
+	assert.Equal(t, f.Name(), "(int64, int64) -> (int64)")
+
+	f.Output = append(f.Output, types.Int64)
+	assert.Equal(t, f.Name(), "(int64, int64) -> (int64, int64)")
+}
\ No newline at end of file
diff --git a/src/types/Parse.go b/src/types/Parse.go
index 1958c1d..00fd0af 100644
--- a/src/types/Parse.go
+++ b/src/types/Parse.go
@@ -6,10 +6,18 @@ import (
 
 // Parse returns the type with the given tokens or `nil` if it doesn't exist.
 func Parse[T ~[]token.Token](tokens T, source []byte) Type {
+	if len(tokens) == 0 {
+		return nil
+	}
+
 	if tokens[0].Kind == token.Mul {
 		to := tokens[1:]
 		typ := Parse(to, source)
 
+		if typ == nil {
+			return nil
+		}
+
 		if typ == Any {
 			return AnyPointer
 		}
@@ -21,6 +29,10 @@ func Parse[T ~[]token.Token](tokens T, source []byte) Type {
 		to := tokens[2:]
 		typ := Parse(to, source)
 
+		if typ == nil {
+			return nil
+		}
+
 		if typ == Any {
 			return AnyArray
 		}
diff --git a/src/types/Parse_test.go b/src/types/Parse_test.go
new file mode 100644
index 0000000..59f4943
--- /dev/null
+++ b/src/types/Parse_test.go
@@ -0,0 +1,56 @@
+package types_test
+
+import (
+	"testing"
+
+	"git.urbach.dev/cli/q/src/token"
+	"git.urbach.dev/cli/q/src/types"
+	"git.urbach.dev/go/assert"
+)
+
+func TestParse(t *testing.T) {
+	tests := []struct {
+		Source       string
+		ExpectedType types.Type
+	}{
+		{"int", types.Int},
+		{"int64", types.Int64},
+		{"int32", types.Int32},
+		{"int16", types.Int16},
+		{"int8", types.Int8},
+		{"uint", types.UInt},
+		{"uint64", types.UInt64},
+		{"uint32", types.UInt32},
+		{"uint16", types.UInt16},
+		{"uint8", types.UInt8},
+		{"byte", types.Byte},
+		{"bool", types.Bool},
+		{"float", types.Float},
+		{"float64", types.Float64},
+		{"float32", types.Float32},
+		{"any", types.Any},
+		{"*any", types.AnyPointer},
+		{"*byte", &types.Pointer{To: types.Byte}},
+		{"[]any", types.AnyArray},
+		{"[]byte", &types.Array{Of: types.Byte}},
+		{"123", nil},
+		{"*", nil},
+		{"[]", nil},
+		{"[", nil},
+		{"_", nil},
+	}
+
+	for _, test := range tests {
+		t.Run(test.Source, func(t *testing.T) {
+			src := []byte(test.Source)
+			tokens := token.Tokenize(src)
+			typ := types.Parse(tokens, src)
+			assert.True(t, types.Is(typ, test.ExpectedType))
+		})
+	}
+}
+
+func TestParseNil(t *testing.T) {
+	tokens := []token.Token(nil)
+	assert.Nil(t, types.Parse(tokens, nil))
+}
\ No newline at end of file