Add test suite and CI workflow

.github/workflows/test.yml

@@ -0,0 +1,32 @@
+name: Tests
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Deno
+        uses: denoland/setup-deno@v2
+        with:
+          deno-version: v2.1.x
+
+      - name: Run tests
+        run: deno task test
+
+      - name: Check formatting
+        run: deno fmt --check
+
+      - name: Run linter
+        run: deno lint

.gitignore

@@ -0,0 +1,22 @@
+# Deno
+.deno/
+deno.lock
+
+# Build outputs
+*.exe
+tile-maker
+
+# Logs
+*.log
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# IDE
+.vscode/
+.idea/
+
+# Test artifacts
+coverage/
+*.lcov

README.md

@@ -2,9 +2,15 @@
 
 ## Problem Statement
 
-When generating tiles for websites, designers and developers often encounter issues when rotating tiles. Common solutions involve less-than-ideal hacks, such as adding pseudoelements, scaling, and rotating them to achieve the desired effect. These workarounds can complicate code, reduce performance, and make maintenance harder.
+When generating tiles for websites, designers and developers often encounter
+issues when rotating tiles. Common solutions involve less-than-ideal hacks, such
+as adding pseudo-elements, scaling, and rotating them to achieve the desired
+effect. These workarounds can complicate code, reduce performance, and make
+maintenance harder.
 
-WTC Tile Maker aims to solve this by providing a robust, programmatic solution for generating and manipulating tiles, including rotation, without relying on CSS hacks.
+WTC Tile Maker aims to solve this by providing a robust, programmatic solution
+for generating and manipulating tiles, including rotation, without relying on
+CSS hacks.
 
 ---
 
@@ -24,10 +30,10 @@ deno run -A main.ts list
 
 # Help
 deno run -A main.ts help
-
 ```
 
-The output file will be saved in the same directory as the input with the angle appended to the filename (e.g., `input-tile-45.png`).
+The output file will be saved in the same directory as the input with the angle
+appended to the filename (e.g., `input-tile-45.png`).
 
 ---
 
@@ -50,6 +56,26 @@ The output file will be saved in the same directory as the input with the angle
    deno run -A main.ts
    ```
 
+### Running Tests
+
+Run the test suite:
+
+```sh
+deno task test
+```
+
+Check code formatting:
+
+```sh
+deno fmt
+```
+
+Run the linter:
+
+```sh
+deno lint
+```
+
 ---
 
 ## CLI Usage
@@ -80,47 +106,49 @@ The output file will be saved in the same directory as the input with the angle
 
 ## Available Rational Angles
 
-These are the angles where `tan(θ) = m/n` for small integers m, n. These angles produce periodic tilings when used for rotation.
-
-| Index | Label                  | m   | n   |
-| ----- | ---------------------- | --- | --- |
-| 0     | 0°                     | 0   | 1   |
-| 1     | 90°                    | 1   | 0   |
-| 2     | -90°                   | -1  | 0   |
-| 3     | 45°                    | 1   | 1   |
-| 4     | -45°                   | -1  | 1   |
-| 5     | 26.565° (arctan 1/2)   | 1   | 2   |
-| 6     | -26.565° (arctan -1/2) | -1  | 2   |
-| 7     | 63.435° (arctan 2)     | 2   | 1   |
-| 8     | -63.435° (arctan -2)   | -2  | 1   |
-| 9     | 18.435° (arctan 1/3)   | 1   | 3   |
-| 10    | -18.435° (arctan -1/3) | -1  | 3   |
-| 11    | 71.565° (arctan 3)     | 3   | 1   |
-| 12    | -71.565° (arctan -3)   | -3  | 1   |
-| 13    | 14.036° (arctan 1/4)   | 1   | 4   |
-| 14    | -14.036° (arctan -1/4) | -1  | 4   |
-| 15    | 75.964° (arctan 4)     | 4   | 1   |
-| 16    | -75.964° (arctan -4)   | -4  | 1   |
-| 17    | 33.690° (arctan 2/3)   | 2   | 3   |
-| 18    | -33.690° (arctan -2/3) | -2  | 3   |
-| 19    | 56.310° (arctan 3/2)   | 3   | 2   |
-| 20    | -56.310° (arctan -3/2) | -3  | 2   |
-| 21    | 36.870° (arctan 3/4)   | 3   | 4   |
-| 22    | -36.870° (arctan -3/4) | -3  | 4   |
-| 23    | 53.130° (arctan 4/3)   | 4   | 3   |
-| 24    | -53.130° (arctan -4/3) | -4  | 3   |
-| 25    | 11.310° (arctan 1/5)   | 1   | 5   |
-| 26    | -11.310° (arctan -1/5) | -1  | 5   |
-| 27    | 78.690° (arctan 5)     | 5   | 1   |
-| 28    | -78.690° (arctan -5)   | -5  | 1   |
+These are the angles where `tan(θ) = m/n` for small integers m, n. These angles
+produce periodic tilings when used for rotation.
+
+| Index | Label                  | m  | n |
+| ----- | ---------------------- | -- | - |
+| 0     | 0°                     | 0  | 1 |
+| 1     | 90°                    | 1  | 0 |
+| 2     | -90°                   | -1 | 0 |
+| 3     | 45°                    | 1  | 1 |
+| 4     | -45°                   | -1 | 1 |
+| 5     | 26.565° (arctan 1/2)   | 1  | 2 |
+| 6     | -26.565° (arctan -1/2) | -1 | 2 |
+| 7     | 63.435° (arctan 2)     | 2  | 1 |
+| 8     | -63.435° (arctan -2)   | -2 | 1 |
+| 9     | 18.435° (arctan 1/3)   | 1  | 3 |
+| 10    | -18.435° (arctan -1/3) | -1 | 3 |
+| 11    | 71.565° (arctan 3)     | 3  | 1 |
+| 12    | -71.565° (arctan -3)   | -3 | 1 |
+| 13    | 14.036° (arctan 1/4)   | 1  | 4 |
+| 14    | -14.036° (arctan -1/4) | -1 | 4 |
+| 15    | 75.964° (arctan 4)     | 4  | 1 |
+| 16    | -75.964° (arctan -4)   | -4 | 1 |
+| 17    | 33.690° (arctan 2/3)   | 2  | 3 |
+| 18    | -33.690° (arctan -2/3) | -2 | 3 |
+| 19    | 56.310° (arctan 3/2)   | 3  | 2 |
+| 20    | -56.310° (arctan -3/2) | -3 | 2 |
+| 21    | 36.870° (arctan 3/4)   | 3  | 4 |
+| 22    | -36.870° (arctan -3/4) | -3 | 4 |
+| 23    | 53.130° (arctan 4/3)   | 4  | 3 |
+| 24    | -53.130° (arctan -4/3) | -4 | 3 |
+| 25    | 11.310° (arctan 1/5)   | 1  | 5 |
+| 26    | -11.310° (arctan -1/5) | -1 | 5 |
+| 27    | 78.690° (arctan 5)     | 5  | 1 |
+| 28    | -78.690° (arctan -5)   | -5 | 1 |
 
 You can also run `deno -A main.ts list` to see these angles.
 
 ---
 
 ## Recommended Input Aspect Ratios
 
-The output tile size depends on how well the input dimensions align with the m:n ratios of the angles. For best results, use these aspect ratios:
+The output tile size depends on how well the input dimensions align with the m:n
+ratios of the angles. For best results, use these aspect ratios:
 
 ### Best Aspect Ratios
 
@@ -136,7 +164,9 @@ The output tile size depends on how well the input dimensions align with the m:n
 
 ### Ratios to Avoid
 
-Aspect ratios with **prime numbers > 5** (like 7:3, 11:4, 13:8) or **irrational proportions** will produce larger outputs because the GCD calculations yield smaller divisors.
+Aspect ratios with **prime numbers > 5** (like 7:3, 11:4, 13:8) or **irrational
+proportions** will produce larger outputs because the GCD calculations yield
+smaller divisors.
 
 ---
 
@@ -156,27 +186,35 @@ deno -A main.ts list
 
 ### Generate a Tile
 
-Generate a rotated tile from `Checker.png` using angle index 27, and max size 6000:
+Generate a rotated tile from `Checker.png` using angle index 27, and max size
+6000:
 
 | Step    | Description                                                                           | Example                                           |
 | ------- | ------------------------------------------------------------------------------------- | ------------------------------------------------- |
 | Input   | Source image to be tiled and rotated.                                                 | <img src="Checker.png" width="300" />             |
 | Command | Command to generate a rotated tile using angle index 27, margin 3, and max size 6000. | `generate -lv -a 27 -s 6000 Checker.png`          |
 | Output  | Resulting seamlessly tileable image after processing.                                 | <img src="Checker-tile-63.435.png" width="300" /> |
 
-This will also work with images of different aspect ratios (like 3×2). For example. this enerates a rotated tile from `3x2-checker.png` using 45°:
+This will also work with images of different aspect ratios (like 3×2). For
+example, this generates a rotated tile from `3x2-checker.png` using 45°:
 
 | Step    | Description                                      | Example                                           |
 | ------- | ------------------------------------------------ | ------------------------------------------------- |
 | Input   | Source image with 3×2 aspect ratio.              | <img src="3x2-checker.png" width="300" />         |
 | Command | Command to generate a rotated tile at 45°.       | `generate -d 45 3x2-checker.png`                  |
 | Output  | Seamlessly tileable image after rotating at 45°. | <img src="3x2-checker-tile-45.png" width="300" /> |
 
-_N.B._ Notice, here, how there seems to be a piece missing! This is because the default tile margin is too small to make these rotated tiles cover the output dimensions. This command should be updated to `generate -m 2 -d 45 3x2-checker.png`.
+_N.B._ Notice, here, how there seems to be a piece missing! This is because the
+default tile margin is too small to make these rotated tiles cover the output
+dimensions. This command should be updated to
+`generate -m 2 -d 45 3x2-checker.png`.
 
 #### A warning about sizes and appropriate aspect ratios
 
-Sometimes, a combination of input size and rotation will produce an output that is either too large or creating an appropriate output tile is just beyong the capabilities of this math. In this case you should likely fall back to hacky methods or get a tile produces in a more predictable aspect ratio.
+Sometimes, a combination of input size and rotation will produce an output that
+is either too large or creating an appropriate output tile is just beyond the
+capabilities of this math. In this case you should likely fall back to hacky
+methods or get a tile produced in a more predictable aspect ratio.
 
 ### Generate with a Specific Degree
 
@@ -192,20 +230,27 @@ The tool will find the closest rational angle and generate the tile accordingly.
 
 ## Common Issues
 
-- **allowLargeBuffers**: If you receive an error about `allowLargeBuffers`, use the `-l` flag. Warning: this may affect performance, but enables processing of narrow rotation / large image combinations.
-- **Missing pieces**: If the output appears to be missing pieces around the edges, try increasing the `-m` (tileMargin) value, e.g., `-m 3`.
+- **allowLargeBuffers**: If you receive an error about `allowLargeBuffers`, use
+  the `-l` flag. Warning: this may affect performance, but enables processing of
+  narrow rotation / large image combinations.
+- **Missing pieces**: If the output appears to be missing pieces around the
+  edges, try increasing the `-m` (tileMargin) value, e.g., `-m 3`.
 
 ---
 
 ## How This Works
 
 ### The Problem with Rotating Tiles
 
-When you rotate a regular tiling pattern (like a checkerboard) by an arbitrary angle, the result doesn't tile seamlessly in the x and y direction anymore.
+When you rotate a regular tiling pattern (like a checkerboard) by an arbitrary
+angle, the result doesn't tile seamlessly in the x and y direction anymore.
 
 ### Rational Angles
 
-The key insight is that **rational angles**—angles where `tan(θ) = m/n` for small integers m and n—produce periodic tilings when used for rotation. At these specific angles, the rotated grid aligns back to integer positions, allowing seamless repetition.
+The key insight is that **rational angles**—angles where `tan(θ) = m/n` for
+small integers m and n—produce periodic tilings when used for rotation. At these
+specific angles, the rotated grid aligns back to integer positions, allowing
+seamless repetition.
 
 For example:
 
@@ -215,21 +260,28 @@ For example:
 
 ### Tile Dimension Calculation
 
-For a rational angle with `tan(θ) = m/n`, the rotated pattern repeats at intervals of `√(m² + n²)` times the original period.
+For a rational angle with `tan(θ) = m/n`, the rotated pattern repeats at
+intervals of `√(m² + n²)` times the original period.
 
 To create a seamlessly tileable output:
 
-- The output dimensions are calculated as: `input dimensions × √(m² + n²) / gcd(m, n)`
+- The output dimensions are calculated as:
+  `input dimensions × √(m² + n²) / gcd(m, n)`
 - This ensures the rotated grid aligns back to integer positions
 
 ### The Process
 
 1. **Input**: A tileable source image (e.g., a checkerboard pattern)
-2. **Tile**: The source image is tiled into a larger canvas to provide enough material for the rotation
+2. **Tile**: The source image is tiled into a larger canvas to provide enough
+   material for the rotation
 3. **Rotate**: The tiled canvas is rotated by the selected rational angle
-4. **Crop**: A precisely calculated region is extracted that will tile seamlessly
-5. **Output**: The resulting image can be used as a CSS background and will tile perfectly at the rotated angle
-
-This approach eliminates the need for CSS hacks like pseudoelements with `transform: rotate()` and `scale()`, resulting in cleaner code, better performance, and more predictable rendering across browsers.
+4. **Crop**: A precisely calculated region is extracted that will tile
+   seamlessly
+5. **Output**: The resulting image can be used as a CSS background and will tile
+   perfectly at the rotated angle
+
+This approach eliminates the need for CSS hacks like pseudo-elements with
+`transform: rotate()` and `scale()`, resulting in cleaner code, better
+performance, and more predictable rendering across browsers.
 
 ---

deno.json

@@ -1,12 +1,14 @@
 {
   "imports": {
+    "@std/assert": "jsr:@std/assert@^1.0.19",
     "@std/cli": "jsr:@std/cli@^1.0.27",
     "@std/fs": "jsr:@std/fs@^1.0.22",
     "@std/path": "jsr:@std/path@^1.1.4",
     "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"
 }