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name: test-common description: Comprehensive testing skill for Common/shared packages. Ensures all reusable components are thoroughly tested with team-wide standards. Use for testing data structures, utilities, pools, and shared libraries.

Test Common Skill

This skill provides comprehensive testing standards for Common/shared packages. Since these packages are used by the entire team, tests must cover ALL possible cases.

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Quality Standards

Metric	Requirement
Line Coverage	Minimum 50% (per project rules)
All Public APIs	Must have tests
Edge Cases	Must be covered
Panic Scenarios	Must be tested
Interface Compliance	Must be verified

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Workflow (Strict 4-Step Process)

Step 1: Business Flow Design

MANDATORY: Analyze EVERY public method in the file.

1. List ALL exported functions/methods
2. For EACH method, identify:
   • Normal usage (happy path)
   • Error conditions
   • Edge cases
   • Panic conditions

Output Format:

## Business Flows: [package/file]

### Method Inventory
| Method | Parameters | Returns | Notes |
|--------|------------|---------|-------|
| New(cap int) | int | *Buffer | Constructor |
| Write(p []byte) | []byte | (int, error) | io.Writer |
| ... | ... | ... | ... |

### Actors
- [List of actors]

### Flows per Method
For each method:
- Happy path
- Error cases
- Edge cases

STOP and wait for user approval.

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Step 2: Test Plan Design

Define testing strategy:

1. Method Coverage Matrix

   • List EVERY public method
   • Assign test count per method (minimum 3 per method)

2. Scope

   • In-scope: All public methods, exposed interfaces
   • Out-of-scope: Private methods, external dependencies

3. Test Types

   • Unit tests (isolated function testing)
   • Integration tests (multi-method workflows)
   • Fuzz tests (if applicable)

4. Interface Compliance

   • List all interfaces the type should implement

Output Format:

### Method Coverage Matrix
| Method | Min Tests | Categories |
|--------|-----------|------------|
| New | 4 | Constructor, Boundary |
| Write | 5 | Input, State, Error |
| Read | 5 | Input, State, Error |
| ... | ... | ... |
| **Total** | **40+** | |

STOP and wait for user approval.

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Step 3: Test Case Design

MANDATORY: Create tests for EVERY method from the inventory.

For EACH method, apply these test categories:

Per-Method Test Matrix

Category	Tests per Method	Description
Happy Path	1-2	Normal valid usage
Nil/Empty Input	1-2	nil, empty slice, ""
Boundary	2-3	min, max, overflow
State	1-2	empty, full, partial
Error/Panic	1-2	Expected failures
Minimum	5-10	Per method

Test Categories Reference

Category 1: Constructor Tests (P0)

Class	Description
Valid Creation	Normal instantiation
Zero/Default	Zero or default values
Negative	Negative values
Nil Config	Nil configuration

Category 2: Input Validation (P0)

Class	Description
Nil Input	nil slice/pointer
Empty Input	empty slice/string
Zero Value	0 for numeric
Negative	-1 where invalid
Overflow	math.MaxInt64

Category 3: Boundary Tests (P0)

Class	Description
Min Value	Minimum valid
Min - 1	Below minimum
Max Value	Maximum valid
Max + 1	Above maximum

Category 4: State Tests (P0)

Class	Description
Empty State	Operations on empty
Full State	Operations on full
Partial State	Mid-state
After Reset	Post-reset
After Release	Post-release

Category 5: Sequence Tests (P1)

Class	Description
Normal Sequence	Expected order
Repeated	Same op multiple times
Interleaved	Alternating operations

Category 6: Error Handling (P1)

Class	Description
Expected Errors	Documented errors
Panic Conditions	Expected panics
Panic Recovery	defer recover()

Category 7: Interface Compliance (P1)

Class	Description
io.Reader	Read interface
io.Writer	Write interface
io.WriterTo	WriteTo interface
io.ReaderFrom	ReadFrom interface

Output Format:

### Test Cases by Method

#### Method: New()
| ID | Category | Input | Expected |
|----|----------|-------|----------|
| TC-New-1 | Happy | New(100) | valid buffer |
| TC-New-2 | Boundary | New(0) | uses default |
| TC-New-3 | Boundary | New(-1) | uses default |
| TC-New-4 | Boundary | New(MAX) | valid buffer |

#### Method: Write()
| ID | Category | Input | Expected |
|----|----------|-------|----------|
| TC-Write-1 | Happy | Write(data) | n=len, nil |
| TC-Write-2 | Nil | Write(nil) | n=0, nil |
| TC-Write-3 | Empty | Write([]byte{}) | n=0, nil |
| TC-Write-4 | Large | Write(1MB) | auto-grow |
| TC-Write-5 | State | Write after Reset | works |

... (repeat for ALL methods)

Verification Checklist:

• Every public method has tests
• Every method has ≥ 5 test cases
• All panic conditions covered
• All error returns covered
• All interfaces verified

STOP and wait for user approval.

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Step 4: Test Code Implementation

Follow these Go testing standards:

File Structure

package_test.go
├── // Interface Compliance (compile-time)
│   var _ io.Writer = (*Type)(nil)
│
├── // Constructor Tests
│   func TestNew(t *testing.T)
│   func TestNew_Defaults(t *testing.T)
│
├── // Method Tests (ONE test function per method)
│   func TestWrite(t *testing.T) - all Write scenarios
│   func TestRead(t *testing.T) - all Read scenarios
│
├── // Sequence Tests
│   func TestWorkflow_NormalSequence(t *testing.T)
│
├── // Panic Tests
│   func TestPanic_NilData(t *testing.T)

Code Patterns

Table-Driven Tests (PREFERRED):

func TestMethod(t *testing.T) {
    tests := []struct {
        name    string
        input   int
        want    int
        wantErr bool
    }{
        {"valid", 100, 100, false},
        {"zero", 0, defaultSize, false},
        {"negative", -1, 0, true},
        // Add ALL cases from test case design
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            got, err := Method(tt.input)
            if (err != nil) != tt.wantErr {
                t.Errorf("error = %v, wantErr %v", err, tt.wantErr)
            }
            if got != tt.want {
                t.Errorf("got = %v, want %v", got, tt.want)
            }
        })
    }
}

Panic Tests:

func TestPanic_Scenario(t *testing.T) {
    defer func() {
        if r := recover(); r == nil {
            t.Error("expected panic")
        }
    }()
    // Code that should panic
}

Interface Compliance:

var _ io.Writer = (*Buffer)(nil)
var _ io.WriterTo = (*Buffer)(nil)
var _ io.ReaderFrom = (*Buffer)(nil)

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Rules (Non-negotiable)

1. Never skip steps - Each step builds on the previous
2. Never assume approval - Always wait for user confirmation
3. Never write code early - Code comes only in Step 4
4. EVERY public method must have tests - No exceptions
5. Minimum 5 tests per method - More for complex methods
6. Test all errors - Every error path must be tested
7. Test all panics - Every panic condition must be verified
8. 50% minimum coverage - Per project requirements

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Priority Definitions

Priority	Description	Must Pass?
P0	Critical functionality	YES - Blocks release
P1	Important scenarios	YES - Should fix
P2	Edge cases	NO - Nice to have

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Approval Prompt

After each step, ask:

"Please review the above and confirm if I should proceed to the next step."