Add tests for getImageProperties function

deno.json

@@ -1,12 +1,14 @@
 {
   "imports": {
-    "@std/cli": "jsr:@std/cli@^1.0.27",
-    "@std/fs": "jsr:@std/fs@^1.0.22",
-    "@std/path": "jsr:@std/path@^1.1.4",
+    "@std/assert": "https://deno.land/std@0.224.0/assert/mod.ts",
+    "@std/cli/parse-args": "https://deno.land/std@0.224.0/cli/parse_args.ts",
+    "@std/fs/exists": "https://deno.land/std@0.224.0/fs/exists.ts",
+    "@std/path": "https://deno.land/std@0.224.0/path/mod.ts",
     "sharp": "npm:sharp@^0.34.5"
   },
   "tasks": {
-    "compile": "deno compile --allow-all main.ts"
+    "compile": "deno compile --allow-all main.ts",
+    "test": "deno test --allow-read --allow-env --allow-ffi"
   },
   "version": "0.0.1"
 }

src/lib.test.ts

@@ -0,0 +1,46 @@
+import { assert, assertEquals, assertRejects } from "@std/assert";
+import { getImageProperties } from "./lib.ts";
+
+Deno.test("getImageProperties - should return correct properties for valid PNG image", async () => {
+  const imagePath = "test.png";
+  const properties = await getImageProperties(imagePath);
+
+  assertEquals(properties.width, 512);
+  assertEquals(properties.height, 512);
+  assertEquals(properties.format, "png");
+});
+
+Deno.test("getImageProperties - should throw error for non-existent file", async () => {
+  const imagePath = "non-existent-file.png";
+
+  await assertRejects(
+    async () => {
+      await getImageProperties(imagePath);
+    },
+    Deno.errors.NotFound,
+  );
+});
+
+Deno.test("getImageProperties - should return correct properties for 3x2 checker image", async () => {
+  const imagePath = "3x2-checker.png";
+  const properties = await getImageProperties(imagePath);
+
+  // Verify it has correct aspect ratio (3:2)
+  assertEquals(properties.format, "png");
+  const aspectRatio = properties.width / properties.height;
+  assertEquals(aspectRatio, 1.5);
+});
+
+Deno.test("getImageProperties - should return properties with valid types", async () => {
+  const imagePath = "test.png";
+  const properties = await getImageProperties(imagePath);
+
+  // Verify property types
+  assertEquals(typeof properties.width, "number");
+  assertEquals(typeof properties.height, "number");
+  assertEquals(typeof properties.format, "string");
+
+  // Verify positive dimensions
+  assert(properties.width > 0);
+  assert(properties.height > 0);
+});