Error Explanation Generator

# Python pytest
pytest -v --tb=long

# JavaScript/TypeScript jest
npm test -- --verbose

# Java junit
mvn test -X

# Go tests
go test -v

FAILED tests/test_user.py::test_create_user - AssertionError: assert 201 == 200

## Error Summary

[One-sentence description of what went wrong]

## What Happened

[Explain the error in plain language]

**Expected:** [What the test expected to happen]
**Actual:** [What actually happened]

## Root Cause

[Explain why this happened - the underlying issue]

## How to Fix

### Option 1: [Most likely fix] ⭐

[Specific code change or action to take]

```[language]
// Before
[problematic code]

// After
[fixed code]

[command to run test]

### Step 6: Suggest Next Steps

Provide actionable guidance:

**If fix is clear:**
- Show exact code change
- Provide test command to verify
- Mention related tests to check

**If diagnosis needs more info:**
- Suggest debugging steps
- Recommend logging/print statements to add
- Propose code to inspect

**If issue is environmental:**
- Suggest dependency checks
- Recommend configuration verification
- Propose environment comparison

## Error Pattern Examples

### Example 1: Assertion Failure (Python/pytest)

**Error Output:**

**Analysis:**

```markdown
## Error Summary
Test expected integer division but got float division result.

## What Happened

**Expected:** `2` (integer)
**Actual:** `2.5` (float)

The test `test_divide` called a divide function with arguments that produce
a decimal result (e.g., 5 / 2 = 2.5) but expected an integer result.

## Root Cause

The implementation uses true division (`/`) which returns floats in Python 3,
but the test expects integer division behavior.

## How to Fix

### Option 1: Update implementation to use integer division ⭐

```python
# Before
def divide(a, b):
    return a / b

# After
def divide(a, b):
    return a // b  # Integer division

# Before
assert divide(5, 2) == 2

# After
assert divide(5, 2) == 2.5

pytest tests/test_calculator.py::test_divide -v

### Example 2: TypeError (JavaScript/Jest)

**Error Output:**

**Analysis:**

```markdown
## Error Summary
Attempted to access property 'name' on undefined user object.

## What Happened

**Expected:** User object with 'name' property
**Actual:** `undefined`

Function `getUserName()` tried to access `.name` property on a value that
was undefined, causing a runtime error.

## Root Cause

The user object passed to `getUserName()` was undefined. This commonly
happens when:
- Function called without argument
- Async data not yet loaded
- Database/API query returned no result

## How to Fix

### Option 1: Add null/undefined check ⭐

```javascript
// Before
function getUserName(user) {
    return user.name;
}

// After
function getUserName(user) {
    if (!user) {
        return null; // or throw error, or return default
    }
    return user.name;
}

// Before
const name = getUserName(); // Called without argument

// After
const name = getUserName({ name: 'Alice', id: 1 });

function getUserName(user) {
    return user?.name ?? 'Unknown';
}

npm test -- user.test.js

### Example 3: Timeout Error (E2E/Cypress)

**Error Output:**

**Analysis:**

```markdown
## Error Summary
Test couldn't find submit button within timeout period.

## What Happened

**Expected:** Element with `data-testid="submit-btn"` to appear on page
**Actual:** Element never appeared within 4 seconds

## Root Cause

Possible reasons:
1. Element takes longer than 4s to render
2. Element has different selector/ID
3. Element only appears under certain conditions
4. JavaScript error preventing element from rendering

## How to Fix

### Option 1: Increase timeout for slow-loading elements ⭐

```javascript
// Before
cy.get('[data-testid="submit-btn"]').click();

// After
cy.get('[data-testid="submit-btn"]', { timeout: 10000 }).click();

// Wait for page to fully load first
cy.get('[data-testid="form-container"]').should('be.visible');
cy.get('[data-testid="submit-btn"]').click();

// Verify element exists with different selector
cy.get('button[type="submit"]').click();

npx cypress run --spec "cypress/e2e/form.cy.js"

### Example 4: Mock Issue (Python/pytest)

**Error Output:**

**Analysis:**

```markdown
## Error Summary
Mock expected a function call that never happened.

## What Happened

**Expected:** `send_email()` to be called with specific arguments
**Actual:** `send_email()` was never called

## Root Cause

The code being tested didn't call the mocked function. Common reasons:
- Different code path executed (conditional logic)
- Function called with different arguments
- Function called on different object instance
- Mock not properly configured

## How to Fix

### Option 1: Verify code path is reached ⭐

```python
# Add debug assertion to check if code executes
def test_registration_sends_email(mocker):
    mock_send = mocker.patch('app.email.send_email')

    result = register_user('user@example.com')

    # Check if registration succeeded
    assert result.success, "Registration failed, email won't be sent"

    mock_send.assert_called_once_with('user@example.com', 'Welcome')

# Ensure you're mocking where it's used, not where it's defined

# Wrong - mocking definition location
mocker.patch('app.email.send_email')

# Right - mocking where it's imported
mocker.patch('app.user.send_email')  # if user.py imports send_email

# Instead of exact match
mock_send.assert_called_once_with('user@example.com', 'Welcome')

# Check if called at all
assert mock_send.called, "send_email was never called"

# Check call happened with first argument matching
mock_send.assert_called()
args = mock_send.call_args[0]
assert args[0] == 'user@example.com'

pytest tests/test_registration.py::test_registration_sends_email -v

print(f"Mock called: {mock_send.called}")
print(f"Call count: {mock_send.call_count}")
print(f"Call args: {mock_send.call_args_list}")

## Framework-Specific Notes

### Python (pytest, unittest)

**Common error patterns:**
- `AssertionError` - Failed assertions
- `AttributeError` - Missing attributes/methods
- `ImportError/ModuleNotFoundError` - Import issues
- `FixtureNotFoundError` - Missing pytest fixtures

**Key files to check:**
- `pytest.ini`, `setup.cfg` - Configuration
- `conftest.py` - Shared fixtures
- `requirements.txt` - Dependencies

### JavaScript/TypeScript (Jest, Mocha, Vitest)

**Common error patterns:**
- `TypeError` - Type-related errors
- `ReferenceError` - Undefined variables
- `Timeout exceeded` - Async operation timeouts
- `Cannot find module` - Import/require issues

**Key files to check:**
- `jest.config.js`, `vitest.config.js` - Test configuration
- `package.json` - Dependencies and scripts
- `tsconfig.json` - TypeScript settings

### Java (JUnit, TestNG)

**Common error patterns:**
- `AssertionFailedError` - Failed assertions
- `NullPointerException` - Null reference access
- `ClassNotFoundException` - Missing classes
- `ComparisonFailure` - Value comparison failures

**Key files to check:**
- `pom.xml` (Maven) or `build.gradle` (Gradle) - Dependencies
- Test configuration annotations

### Go (testing package)

**Common error patterns:**
- Test panics - Runtime panics
- Comparison failures - Expected vs actual mismatches
- Race conditions - Data race detector failures

**Key commands:**
```bash
go test -v              # Verbose output
go test -race           # Race detection
go test -cover          # Coverage