Selfie

https://selfie.dev
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Selfie is a snapshot testing framework for JVM, Python, and JavaScript. It enables efficient and...
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### Selfie Disk Snapshot for Binary Content (GZIP)

Source: https://selfie.dev/index

This example shows how Selfie can store binary content, such as a gzipped favicon, as a disk snapshot. `toMatchDisk()` saves the snapshot to a file, which is suitable for large or non-textual data.

```java
@Test
public void gzipFavicon() {
    expectSelfie(get("/favicon.ico", ContentEncoding.GZIP)).toMatchDisk();
}
```

--------------------------------

### Example Content of a Selfie Disk Snapshot File (.ss)

Source: https://selfie.dev/index

This snippet illustrates the structure and content of a `.ss` snapshot file generated by Selfie. It shows how multiple named snapshots and their content are stored within a single file, including base64 encoded binary data and HTML, separated by `\n╔═` delimiters.

```text
╔═ gzipFavicon ═╗ base64 length 12 bytes
Umlja1JvbGwuanBn
╔═ orderFlow/initial ═╗
<html><body>
  <button>Submit order</button>
</body></html>
╔═ orderFlow/ordered ═╗
<html><body>
  <p>Thanks for your business!</p>
  <details>
    <summary>Order information</summary>
    <p>Tracking #ABC123</p>
  </details>
</body></html>
```

--------------------------------

### Caching Binary Data with `cacheSelfieBinary`

Source: https://selfie.dev/index

This Java example illustrates how `cacheSelfieBinary` can be used to cache binary data, such as an image generated by an AI service. The cached binary data can then be saved directly to a file, streamlining tests that involve binary outputs.

```Java
var imageBytes = cacheSelfieBinary(() -> {
  return client.generateImage("A robot making a self portrait");
}).toBeFile("selfie.png")
```

--------------------------------

### Traditional JUnit Test with Assertions

Source: https://selfie.dev/index

This JUnit test demonstrates a common approach to testing, asserting properties of a list of prime numbers. It uses `assertThat` for traditional, explicit assertions on the start and end elements of the list.

```java
@Test
public void primesBelow100() {
  Assertions.assertThat(primesBelow(100)).startsWith(2, 3, 5, 7).endsWith(89, 97);
}
```

--------------------------------

### Adding a Markdown Facet to a Snapshot

Source: https://selfie.dev/index

This example demonstrates how to add a 'facet' to a snapshot, providing an alternative view of the subject. Here, HTML content is transformed into Markdown using `HtmlToMdParser.parse(html)` and stored as an 'md' facet alongside the original HTML.

```java
var html = "<html>..."
var snapshot = Snapshot.of(html).plusFacet("md", HtmlToMdParser.parse(html))
expectSelfie(snapshot).toMatchDisk()
```

--------------------------------

### Testing with Facets in Multi-Stage Workflows

Source: https://selfie.dev/index

This test combines disk snapshots with facets to capture different views of the order flow at various stages. It asserts both the full HTML content (via `toMatchDisk`) and a simplified Markdown view (via `facet("md").toBe`), making tests more comprehensive and readable.

```java
@Test
public void orderFlow() {
  expectSelfie(get("/orders")).toMatchDisk("initial")
    .facet("md").toBe("Submit order");
  postOrder();
  expectSelfie(get("/orders")).toMatchDisk("ordered")
    .facet("md").toBe("Thanks for your business!");
}
```

--------------------------------

### Selfie Literal Snapshot with Initial TODO State

Source: https://selfie.dev/index

This test demonstrates the initial usage of Selfie's literal snapshots. `expectSelfie` captures the output of `primesBelow(100).toString()`, and `toBe_TODO()` marks the snapshot for automatic population by Selfie upon the first test run.

```java
@Test
public void primesBelow100() {
  expectSelfie(primesBelow(100).toString()).toBe_TODO();
}
```

--------------------------------

### Selfie Core API: Snapshot, Lens, Camera Interfaces

Source: https://selfie.dev/index

This section outlines the core interfaces and classes in the Selfie library for managing snapshots and transformations. It defines `Snapshot` with its subject and facets, `Lens` for transforming snapshots, and `Camera` for creating snapshots with optional lenses, forming the foundation of Selfie's lensable capabilities.

```APIDOC
final class Snapshot {
  final SnapshotValue subject;
  final ImmutableSortedMap<String, SnapshotValue> facets;
}
interface Lens {
  Snapshot transform(Snapshot snapshot);
}
interface Camera<T> {
  Snapshot snapshot(T subject);
  default Camera<T> withLens(Lens lens) {
    // returns a new Camera which applies the given lens to every snapshot
  }
}
```

--------------------------------

### Selfie Disk Snapshots for Multi-Stage Workflow

Source: https://selfie.dev/index

This test uses named disk snapshots to capture the state of an order flow at different stages ('initial' and 'ordered'). This allows tracking changes in complex workflows over time by comparing distinct snapshots.

```java
@Test
public void orderFlow() {
  expectSelfie(get("/orders")).toMatchDisk("initial");
  postOrder();
  expectSelfie(get("/orders")).toMatchDisk("ordered");
}
```

--------------------------------

### Debugging with System.out.println in JUnit

Source: https://selfie.dev/index

This snippet illustrates a common debugging technique where the output of a function is printed to the console. While useful for quick inspection, this method lacks repeatability and formal assertion, making it unsuitable for automated tests.

```java
@Test
public void testMcTestFace() {
  System.out.println(primesBelow(100));
}
```

--------------------------------

### Caching String API Responses with `cacheSelfie`

Source: https://selfie.dev/index

This Java code demonstrates using `cacheSelfie` to store and retrieve string-based responses from an `ExpensiveAiService`. It captures the output of an AI chat interaction, allowing it to be mocked in subsequent test runs, ensuring consistent and fast test execution.

```Java
var client = ExpensiveAiService();
var chatResponse = cacheSelfie(() -> {
  return client.chat("What's your favorite number today?");
}).toBe("Since it's March 14, my favorite number is π")
// build other stuff with the chat response
```

--------------------------------

### Selfie Literal Snapshot After Auto-Population

Source: https://selfie.dev/index

After the initial run, Selfie automatically rewrites `_TODO()` with the actual value, turning the `println`-like output into a proper, repeatable assertion. This eliminates manual assertion writing and ensures completeness.

```java
@Test
public void primesBelow100() {
  expectSelfie(primesBelow(100).toString())
    .toBe("[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]");
}
```
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