Move out interface definitions

Author: cblanc

test/unit.ts

@@ -1,23 +1,8 @@
 import { assert } from "chai";
 import Postcode from "../lib/index";
-import { loadFixtures, TestCase } from "./util/helper";
-
-type Method =
-  | "normalise"
-  | "incode"
-  | "outcode"
-  | "area"
-  | "district"
-  | "unit"
-  | "sector"
-  | "subDistrict";
-
-interface TestMethodOptions {
-  tests: TestCase[];
-  method: Method;
-}
-
-const testMethod = (options: TestMethodOptions): void => {
+import { loadFixtures, TestMethod } from "./util/helper";
+
+const testMethod: TestMethod = options => {
   const { tests, method } = options;
   tests.forEach(({ base, expected }) => {
     const p = new Postcode(base);

test/util/helper.ts

@@ -1,6 +1,25 @@
 import { join } from "path";
 import { readFile } from "fs";
 
+type PostcodeMethod =
+  | "normalise"
+  | "incode"
+  | "outcode"
+  | "area"
+  | "district"
+  | "unit"
+  | "sector"
+  | "subDistrict";
+
+interface TestMethodOptions {
+  tests: TestCase[];
+  method: PostcodeMethod;
+}
+
+export interface TestMethod {
+  (options: TestMethodOptions): void;
+}
+
 const dataDir = join(__dirname, "../data");
 
 interface TestFixtures {