diff --git a/Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeConverterTests.swift b/Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeConverterTests.swift
new file mode 100644
index 0000000..d312aec
--- /dev/null
+++ b/Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeConverterTests.swift
@@ -0,0 +1,106 @@
+import XCTest
+import CodableToTypeScript
+import SwiftTypeReader
+import TypeScriptAST
+
+final class GenerateCustomTypeConverterTests: GenerateTestCaseBase {
+    /*
+     Use TypeMap instead of custom TypeConverter as much as possible
+     */
+    struct CustomConverter: TypeConverter {
+        var generator: CodeGenerator
+        var swiftType: any SType
+
+        func name(for target: GenerationTarget) throws -> String {
+            switch target {
+            case .entity: return "Custom"
+            case .json: return try `default`.name(for: .json)
+            }
+        }
+
+        func typeDecl(for target: GenerationTarget) throws -> TSTypeDecl? {
+            return nil
+        }
+
+        func hasDecode() throws -> Bool {
+            return true
+        }
+
+        func decodeName() throws -> String {
+            return "Custom_decode"
+        }
+
+        func decodeDecl() throws -> TSFunctionDecl? {
+            return nil
+        }
+
+        func hasEncode() throws -> Bool {
+            return true
+        }
+
+        func encodeName() throws -> String {
+            return "Custom_encode"
+        }
+
+        func encodeDecl() throws -> TSFunctionDecl? {
+            return nil
+        }
+    }
+
+    func testCustomTypeConverter() throws {
+        let typeConverterProvider = TypeConverterProvider { (gen, type) in
+            let repr = type.toTypeRepr(containsModule: false)
+            if let ident = repr.asIdent,
+               let element = ident.elements.last,
+               element.name == "Custom"
+            {
+                return CustomConverter(generator: gen, swiftType: type)
+            }
+            return nil
+        }
+
+        try assertGenerate(
+            source: """
+struct S {
+    var a: Custom
+    var b: [Custom]
+    var c: [[Custom]]
+}
+""",
+        typeConverterProvider: typeConverterProvider,
+        expecteds: ["""
+export type S = {
+    a: Custom;
+    b: Custom[];
+    c: Custom[][];
+};
+""", """
+export type S_JSON = {
+    a: Custom_JSON;
+    b: Custom_JSON[];
+    c: Custom_JSON[][];
+};
+""", """
+export function S_decode(json: S_JSON): S {
+    return {
+        a: Custom_decode(json.a),
+        b: Array_decode(json.b, Custom_decode),
+        c: Array_decode(json.c, (json: Custom_JSON[]): Custom[] => {
+            return Array_decode(json, Custom_decode);
+        })
+    };
+}
+""", """
+export function S_encode(entity: S): S_JSON {
+    return {
+        a: Custom_encode(entity.a),
+        b: Array_encode(entity.b, Custom_encode),
+        c: Array_encode(entity.c, (entity: Custom[]): Custom_JSON[] => {
+            return Array_encode(entity, Custom_encode);
+        })
+    };
+}
+"""
+                   ]
+        )
+    }}
diff --git a/Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeTests.swift b/Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeMapTests.swift
similarity index 71%
rename from Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeTests.swift
rename to Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeMapTests.swift
index 982237d..8495270 100644
--- a/Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeTests.swift
+++ b/Tests/CodableToTypeScriptTests/Generate/GenerateCustomTypeMapTests.swift
@@ -3,7 +3,7 @@ import CodableToTypeScript
 import SwiftTypeReader
 import TypeScriptAST
 
-final class GenerateCustomTypeTests: GenerateTestCaseBase {
+final class GenerateCustomTypeMapTests: GenerateTestCaseBase {
     func testCustomName() throws {
         var typeMap = TypeMap.default
         typeMap.table["URL"] = .init(name: "string")
@@ -252,105 +252,6 @@ export type S = {
         )
     }
 
-
-    struct DateConverter: TypeConverter {
-        var generator: CodeGenerator
-        var swiftType: any SType
-        
-        func name(for target: GenerationTarget) throws -> String {
-            switch target {
-            case .entity: return "Date"
-            case .json: return try `default`.name(for: .json)
-            }
-        }
-
-        func typeDecl(for target: GenerationTarget) throws -> TSTypeDecl? {
-            return nil
-        }
-
-        func hasDecode() throws -> Bool {
-            return true
-        }
-
-        func decodeName() throws -> String {
-            return "Date_decode"
-        }
-
-        func decodeDecl() throws -> TSFunctionDecl? {
-            return nil
-        }
-
-        func hasEncode() throws -> Bool {
-            return true
-        }
-
-        func encodeName() throws -> String {
-            return "Date_encode"
-        }
-
-        func encodeDecl() throws -> TSFunctionDecl? {
-            return nil
-        }
-    }
-
-    func testCustomTypeConverter() throws {
-        let typeConverterProvider = TypeConverterProvider { (gen, type) in
-            let repr = type.toTypeRepr(containsModule: false)
-            if let ident = repr.asIdent,
-               let element = ident.elements.last,
-               element.name == "Date"
-            {
-                return DateConverter(generator: gen, swiftType: type)
-            }
-            return nil
-        }
-
-        try assertGenerate(
-            source: """
-struct S {
-    var a: Date
-    var b: [Date]
-    var c: [[Date]]
-}
-""",
-        typeConverterProvider: typeConverterProvider,
-        expecteds: ["""
-export type S = {
-    a: Date;
-    b: Date[];
-    c: Date[][];
-};
-""", """
-export type S_JSON = {
-    a: Date_JSON;
-    b: Date_JSON[];
-    c: Date_JSON[][];
-};
-""", """
-export function S_decode(json: S_JSON): S {
-    return {
-        a: Date_decode(json.a),
-        b: Array_decode(json.b, Date_decode),
-        c: Array_decode(json.c, (json: Date_JSON[]): Date[] => {
-            return Array_decode(json, Date_decode);
-        })
-    };
-}
-""", """
-export function S_encode(entity: S): S_JSON {
-    return {
-        a: Date_encode(entity.a),
-        b: Array_encode(entity.b, Date_encode),
-        c: Array_encode(entity.c, (entity: Date[]): Date_JSON[] => {
-            return Array_encode(entity, Date_encode);
-        })
-    };
-}
-"""
-                   ]
-        )
-    }
-
     func testMapUserType() throws {
         var typeMap = TypeMap()
         typeMap.table["S"] = .init(name: "V")