test(cache): test the cacher

src/write.test.ts

@@ -1,7 +1,83 @@
 import { describe, expect, test } from "vitest";
+import { updateCache } from "./write";
 
-describe("write to file", () => {
-	test("Hello", () => {
-		expect(true).toBeTruthy();
+describe("cache", () => {
+	test("writes output to empty cache", () => {
+		const cache = {};
+
+		updateCache({
+			cache,
+			data: {
+				Test: new Set(["hello"]),
+				"Test.NestedNamespace": new Set(["foobar"]),
+			},
+			source: {},
+		});
+
+		expect(cache).toEqual({
+			Test: {
+				hello: "Test.hello",
+				NestedNamespace: {
+					foobar: "Test.NestedNamespace.foobar",
+				},
+			},
+		});
+	});
+
+	test("writes output to existing cache", () => {
+		const cache = {
+			Test: {
+				hello: "Test.hello",
+				NestedNamespace: {
+					foobar: "Test.NestedNamespace.foobar",
+				},
+			},
+		};
+
+		updateCache({
+			cache,
+			data: {
+				Test: new Set(["test"]),
+				"Test.NestedNamespace": new Set(["test"]),
+			},
+			source: {},
+		});
+
+		expect(cache).toEqual({
+			Test: {
+				hello: "Test.hello",
+				test: "Test.test",
+				NestedNamespace: {
+					foobar: "Test.NestedNamespace.foobar",
+					test: "Test.NestedNamespace.test",
+				},
+			},
+		});
+	});
+
+	test("updates labels with existing source", () => {
+		const cache = {};
+
+		updateCache({
+			cache,
+			data: {
+				Test: new Set(["hello"]),
+				"Test.NestedNamespace": new Set(["foobar"]),
+			},
+			source: {
+				Test: {
+					hello: "Hello",
+				},
+			},
+		});
+
+		expect(cache).toEqual({
+			Test: {
+				hello: "Hello",
+				NestedNamespace: {
+					foobar: "Test.NestedNamespace.foobar",
+				},
+			},
+		});
 	});
 });

src/write.ts

@@ -63,7 +63,7 @@ export async function processFiles(
 /**
  * Update existing cache based on given data and source labels
  */
-function updateCache({
+export function updateCache({
 	cache,
 	source,
 	data,