diff --git a/README.md b/README.md
index 3471b24..130f818 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,20 @@ The output file will be saved in the same directory as the input with the angle
    deno run -A main.ts
    ```
 
+### Running Tests
+
+To run the test suite:
+
+```sh
+deno task test
+```
+
+Or run tests directly:
+
+```sh
+deno test --allow-all
+```
+
 ---
 
 ## CLI Usage
diff --git a/deno.json b/deno.json
index b61140f..1b61968 100644
--- a/deno.json
+++ b/deno.json
@@ -6,7 +6,8 @@
     "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-all"
   },
   "version": "0.0.1"
 }
diff --git a/main.ts b/main.ts
index 7815a2a..705bed1 100644
--- a/main.ts
+++ b/main.ts
@@ -132,7 +132,7 @@ export interface GenerateOptions {
   input?: string;
 }
 
-async function generate({
+export async function generate({
   angleOption = 0,
   degrees,
   output,
diff --git a/main_test.ts b/main_test.ts
new file mode 100644
index 0000000..23b1795
--- /dev/null
+++ b/main_test.ts
@@ -0,0 +1,223 @@
+import { assertEquals, assertRejects } from "jsr:@std/assert";
+import { existsSync } from "@std/fs/exists";
+import { generate, GenerateOptions } from "./main.ts";
+
+// Create a temporary test image for testing
+async function createTestImage(path: string) {
+  // Create a simple 100x100 PNG for testing
+  const sharp = (await import("sharp")).default;
+  await sharp({
+    create: {
+      width: 100,
+      height: 100,
+      channels: 4,
+      background: { r: 255, g: 0, b: 0, alpha: 1 },
+    },
+  })
+    .png()
+    .toFile(path);
+}
+
+// Clean up test files
+async function cleanupTestFiles(paths: string[]) {
+  for (const path of paths) {
+    try {
+      if (existsSync(path)) {
+        await Deno.remove(path);
+      }
+    } catch {
+      // Ignore cleanup errors
+    }
+  }
+}
+
+Deno.test("generate - successful generation with default angleOption", async () => {
+  const testInput = "/tmp/test-input-default.png";
+  const expectedOutput = "/tmp/test-input-default-tile-0.png";
+
+  try {
+    // Create test input image
+    await createTestImage(testInput);
+
+    // Generate tile with default options
+    await generate({
+      input: testInput,
+      angleOption: 0,
+      maxValidSize: 2000,
+    } as GenerateOptions);
+
+    // Verify output file was created
+    assertEquals(existsSync(expectedOutput), true);
+  } finally {
+    await cleanupTestFiles([testInput, expectedOutput]);
+  }
+});
+
+Deno.test("generate - successful generation with degrees parameter", async () => {
+  const testInput = "/tmp/test-input-degrees.png";
+  const expectedOutput = "/tmp/test-input-degrees-tile-45.png";
+
+  try {
+    // Create test input image
+    await createTestImage(testInput);
+
+    // Generate tile with degrees parameter
+    await generate({
+      input: testInput,
+      degrees: 45,
+      maxValidSize: 2000,
+    } as GenerateOptions);
+
+    // Verify output file was created
+    assertEquals(existsSync(expectedOutput), true);
+  } finally {
+    await cleanupTestFiles([testInput, expectedOutput]);
+  }
+});
+
+Deno.test("generate - error when input file is missing", async () => {
+  await assertRejects(
+    async () => {
+      await generate({
+        maxValidSize: 2000,
+      } as GenerateOptions);
+    },
+    Error,
+    "Input file is required for generation.",
+  );
+});
+
+Deno.test("generate - error when input file doesn't exist", async () => {
+  await assertRejects(
+    async () => {
+      await generate({
+        input: "/tmp/nonexistent-file.png",
+        maxValidSize: 2000,
+      } as GenerateOptions);
+    },
+    Error,
+    "Input file not found:",
+  );
+});
+
+Deno.test("generate - error when angleOption is out of range (negative)", async () => {
+  const testInput = "/tmp/test-input-negative-angle.png";
+
+  try {
+    await createTestImage(testInput);
+
+    await assertRejects(
+      async () => {
+        await generate({
+          input: testInput,
+          angleOption: -1,
+          maxValidSize: 2000,
+        } as GenerateOptions);
+      },
+      Error,
+      "Invalid angle index",
+    );
+  } finally {
+    await cleanupTestFiles([testInput]);
+  }
+});
+
+Deno.test("generate - error when angleOption is out of range (too large)", async () => {
+  const testInput = "/tmp/test-input-large-angle.png";
+
+  try {
+    await createTestImage(testInput);
+
+    await assertRejects(
+      async () => {
+        await generate({
+          input: testInput,
+          angleOption: 999,
+          maxValidSize: 2000,
+        } as GenerateOptions);
+      },
+      Error,
+      "Invalid angle index",
+    );
+  } finally {
+    await cleanupTestFiles([testInput]);
+  }
+});
+
+Deno.test("generate - error when dimensions exceed maxValidSize", async () => {
+  const testInput = "/tmp/test-input-exceed-size.png";
+
+  try {
+    // Create a larger test image
+    const sharp = (await import("sharp")).default;
+    await sharp({
+      create: {
+        width: 500,
+        height: 500,
+        channels: 4,
+        background: { r: 255, g: 0, b: 0, alpha: 1 },
+      },
+    })
+      .png()
+      .toFile(testInput);
+
+    await assertRejects(
+      async () => {
+        await generate({
+          input: testInput,
+          angleOption: 7, // 63.435° - will produce larger dimensions
+          maxValidSize: 100, // Very small max size to trigger error
+        } as GenerateOptions);
+      },
+      Error,
+      "exceed maximum valid size",
+    );
+  } finally {
+    await cleanupTestFiles([testInput]);
+  }
+});
+
+Deno.test("generate - successful generation with custom output path", async () => {
+  const testInput = "/tmp/test-input-custom-output.png";
+  const customOutput = "/tmp/custom-output-name.png";
+
+  try {
+    // Create test input image
+    await createTestImage(testInput);
+
+    // Generate tile with custom output path
+    await generate({
+      input: testInput,
+      angleOption: 3, // 45 degrees
+      output: customOutput,
+      maxValidSize: 2000,
+    } as GenerateOptions);
+
+    // Verify custom output file was created
+    assertEquals(existsSync(customOutput), true);
+  } finally {
+    await cleanupTestFiles([testInput, customOutput]);
+  }
+});
+
+Deno.test("generate - generation with specific angle options", async () => {
+  const testInput = "/tmp/test-input-angle-option.png";
+  const expectedOutput = "/tmp/test-input-angle-option-tile-26.565.png";
+
+  try {
+    // Create test input image
+    await createTestImage(testInput);
+
+    // Generate tile with angle option 5 (26.565°)
+    await generate({
+      input: testInput,
+      angleOption: 5,
+      maxValidSize: 2000,
+    } as GenerateOptions);
+
+    // Verify output file was created
+    assertEquals(existsSync(expectedOutput), true);
+  } finally {
+    await cleanupTestFiles([testInput, expectedOutput]);
+  }
+});