1 files changed, 33 insertions, 0 deletions
diff --git a/test/base.ts b/test/base.ts
index 8369bfe..064ed57 100644
--- a/test/base.ts
+++ b/test/base.ts
@@ -1,14 +1,19 @@
 export { assertEquals } from "https://deno.land/std@0.193.0/testing/asserts.ts";
 
+import { diffCharacters } from "https://deno.land/x/diff@v0.3.5/mod.ts";
+import { bold, gray, green, red } from "https://deno.land/std@0.193.0/fmt/colors.ts";
+
 import Yomikun from "../api/yomikun.ts";
 import DirectCoreClient from '../core/direct/client.ts';
 import { Wrap } from "../util/wrap.ts";
+import YomikunError from "../util/error.ts";
 
 export const core = new DirectCoreClient();
 export const api = new Yomikun(core);
 
 await api.ready;
 
+/** @summary print padded test case index (e.g. "(001/452)") */
 export function formatCaseIndex(i: number, total: number) {
 	let out = "";
 	out += (i+1).toString().padStart(Math.log10(total) + 1, '0');
@@ -16,3 +21,31 @@ export function formatCaseIndex(i: number, total: number) {
 	out += total.toString();
 	return out.wrap(Wrap.parenthesis);
 }
+
+/** @summary diff a (single line) string character by character and insert ANSI color codes */
+export function strDiff(expected: string, actual: string): string {
+	let out = "";
+	const diff = diffCharacters(expected, actual);
+	out += "expected: ";
+	out += diff.filter(c => c.wasAdded == false).map(c => c.wasRemoved ? red(c.character) : bold(gray(c.character))).join("");
+	out += "\n";
+	out += "  actual: ";
+	out += diff.filter(c => c.wasRemoved == false).map(c => c.wasAdded ? green(c.character) : bold(gray(c.character))).join("");
+	return out;
+}
+
+export function assertStrDiffMsg(expected: string, actual: string): string {
+	let msg = "Values are not equal!\n\n";
+	msg += "  ";
+	msg += bold(gray("[diff]")) + "  " + `(${red("removed")}/${green("added")})`;
+	msg += "\n";
+	msg += strDiff(expected, actual);
+	return msg;
+}
+
+/** @summary like deno std assertEquals but character by character */
+export function assertStrDiff(expected: string, actual: string): void | never {
+	if (expected == actual) return;
+	throw new YomikunError(assertStrDiffMsg(expected, actual));
+}
+