1 files changed, 111 insertions, 0 deletions
diff --git a/std/testing/_diff_test.ts b/std/testing/_diff_test.ts
new file mode 100644
index 000000000..211a34c34
--- /dev/null
+++ b/std/testing/_diff_test.ts
@@ -0,0 +1,111 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { diff } from "./_diff.ts";
+import { assertEquals } from "../testing/asserts.ts";
+
+Deno.test({
+  name: "empty",
+  fn(): void {
+    assertEquals(diff([], []), []);
+  },
+});
+
+Deno.test({
+  name: '"a" vs "b"',
+  fn(): void {
+    assertEquals(diff(["a"], ["b"]), [
+      { type: "removed", value: "a" },
+      { type: "added", value: "b" },
+    ]);
+  },
+});
+
+Deno.test({
+  name: '"a" vs "a"',
+  fn(): void {
+    assertEquals(diff(["a"], ["a"]), [{ type: "common", value: "a" }]);
+  },
+});
+
+Deno.test({
+  name: '"a" vs ""',
+  fn(): void {
+    assertEquals(diff(["a"], []), [{ type: "removed", value: "a" }]);
+  },
+});
+
+Deno.test({
+  name: '"" vs "a"',
+  fn(): void {
+    assertEquals(diff([], ["a"]), [{ type: "added", value: "a" }]);
+  },
+});
+
+Deno.test({
+  name: '"a" vs "a, b"',
+  fn(): void {
+    assertEquals(diff(["a"], ["a", "b"]), [
+      { type: "common", value: "a" },
+      { type: "added", value: "b" },
+    ]);
+  },
+});
+
+Deno.test({
+  name: '"strength" vs "string"',
+  fn(): void {
+    assertEquals(diff(Array.from("strength"), Array.from("string")), [
+      { type: "common", value: "s" },
+      { type: "common", value: "t" },
+      { type: "common", value: "r" },
+      { type: "removed", value: "e" },
+      { type: "added", value: "i" },
+      { type: "common", value: "n" },
+      { type: "common", value: "g" },
+      { type: "removed", value: "t" },
+      { type: "removed", value: "h" },
+    ]);
+  },
+});
+
+Deno.test({
+  name: '"strength" vs ""',
+  fn(): void {
+    assertEquals(diff(Array.from("strength"), Array.from("")), [
+      { type: "removed", value: "s" },
+      { type: "removed", value: "t" },
+      { type: "removed", value: "r" },
+      { type: "removed", value: "e" },
+      { type: "removed", value: "n" },
+      { type: "removed", value: "g" },
+      { type: "removed", value: "t" },
+      { type: "removed", value: "h" },
+    ]);
+  },
+});
+
+Deno.test({
+  name: '"" vs "strength"',
+  fn(): void {
+    assertEquals(diff(Array.from(""), Array.from("strength")), [
+      { type: "added", value: "s" },
+      { type: "added", value: "t" },
+      { type: "added", value: "r" },
+      { type: "added", value: "e" },
+      { type: "added", value: "n" },
+      { type: "added", value: "g" },
+      { type: "added", value: "t" },
+      { type: "added", value: "h" },
+    ]);
+  },
+});
+
+Deno.test({
+  name: '"abc", "c" vs "abc", "bcd", "c"',
+  fn(): void {
+    assertEquals(diff(["abc", "c"], ["abc", "bcd", "c"]), [
+      { type: "common", value: "abc" },
+      { type: "added", value: "bcd" },
+      { type: "common", value: "c" },
+    ]);
+  },
+});