# Sprint 63 Kickoff: Multi-Language Mutation Testing Support

**Sprint Duration**: 3 days
**Target Version**: v2.176.0
**Start Date**: October 27, 2025 (after Sprint 62 completion)
**Focus**: Extend mutation testing from Rust-only to support Python, TypeScript, Go, and C++

---

## Sprint Goals

### Primary Goal
Expand `pmat mutate` to support **5 languages** with production-ready mutation operators:
1. **Rust** (already implemented in v2.175.0)
2. **Python** (NEW)
3. **TypeScript/JavaScript** (NEW)
4. **Go** (NEW)
5. **C++** (NEW)

### Success Criteria
- ✅ Language auto-detection from file extensions
- ✅ 5-10 mutation operators per language
- ✅ Integration tests for all 5 languages
- ✅ Documentation updated with language-specific examples
- ✅ Performance comparable to Rust implementation

---

## Architecture Overview

### Current State (v2.175.0)
```
pmat mutate
  └── server/src/services/mutation/
      ├── engine.rs                          # Generic mutation engine
      ├── types.rs                           # Mutant, MutantStatus enums
      ├── rust_tree_sitter_mutations.rs      # Rust-specific mutations
      └── rust_adapter.rs                    # Cargo test runner
```

**Rust-only**: All mutation logic hardcoded for Rust syntax

### Target State (v2.176.0)
```
pmat mutate
  └── server/src/services/mutation/
      ├── engine.rs                          # Generic mutation engine (updated)
      ├── types.rs                           # Mutant, MutantStatus enums (unchanged)
      ├── language_detector.rs               # NEW: Auto-detect language from file
      ├── operators/                         # NEW: Per-language mutation operators
      │   ├── mod.rs                         # Trait: MutationOperator
      │   ├── rust.rs                        # Rust operators (refactored from rust_tree_sitter_mutations.rs)
      │   ├── python.rs                      # Python operators
      │   ├── typescript.rs                  # TypeScript/JavaScript operators
      │   ├── go.rs                          # Go operators
      │   └── cpp.rs                         # C++ operators
      └── adapters/                          # NEW: Per-language test runners
          ├── mod.rs                         # Trait: TestAdapter
          ├── rust.rs                        # Cargo test runner (refactored from rust_adapter.rs)
          ├── python.rs                      # pytest/unittest runner
          ├── typescript.rs                  # Jest/Mocha runner
          ├── go.rs                          # go test runner
          └── cpp.rs                         # gtest/Catch2 runner
```

**Multi-language**: Plugin architecture with language-specific implementations

---

## Implementation Plan

### Day 1: Architecture Refactoring + Python Support

#### Task 1: Create Language Detection Module (1 hour)
**File**: `server/src/services/mutation/language_detector.rs`

```rust
use std::path::Path;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Language {
    Rust,
    Python,
    TypeScript,
    JavaScript,
    Go,
    Cpp,
    Unsupported,
}

impl Language {
    pub fn from_extension(path: &Path) -> Self {
        match path.extension().and_then(|e| e.to_str()) {
            Some("rs") => Language::Rust,
            Some("py") => Language::Python,
            Some("ts") => Language::TypeScript,
            Some("tsx") => Language::TypeScript,
            Some("js") => Language::JavaScript,
            Some("jsx") => Language::JavaScript,
            Some("go") => Language::Go,
            Some("cpp") | Some("cc") | Some("cxx") | Some("hpp") | Some("hxx") => Language::Cpp,
            _ => Language::Unsupported,
        }
    }

    pub fn name(&self) -> &'static str {
        match self {
            Language::Rust => "Rust",
            Language::Python => "Python",
            Language::TypeScript => "TypeScript",
            Language::JavaScript => "JavaScript",
            Language::Go => "Go",
            Language::Cpp => "C++",
            Language::Unsupported => "Unsupported",
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_rust_detection() {
        assert_eq!(Language::from_extension(Path::new("foo.rs")), Language::Rust);
    }

    #[test]
    fn test_python_detection() {
        assert_eq!(Language::from_extension(Path::new("foo.py")), Language::Python);
    }

    #[test]
    fn test_typescript_detection() {
        assert_eq!(Language::from_extension(Path::new("foo.ts")), Language::TypeScript);
        assert_eq!(Language::from_extension(Path::new("foo.tsx")), Language::TypeScript);
    }
}
```

#### Task 2: Define Operator and Adapter Traits (1 hour)
**File**: `server/src/services/mutation/operators/mod.rs`

```rust
use crate::services::mutation::types::{Mutant, MutantStatus};
use std::path::Path;

pub mod rust;
pub mod python;
pub mod typescript;
pub mod go;
pub mod cpp;

/// Trait for language-specific mutation operators
pub trait MutationOperator {
    /// Generate mutants for a given source file
    fn generate_mutants(&self, source: &str, file_path: &Path) -> Result<Vec<Mutant>, String>;

    /// Apply a mutant to source code
    fn apply_mutant(&self, source: &str, mutant: &Mutant) -> Result<String, String>;
}

/// Trait for language-specific test adapters
pub trait TestAdapter {
    /// Run tests for a mutated file
    fn run_tests(&self, mutated_source: &str, original_file: &Path) -> Result<MutantStatus, String>;

    /// Get test timeout in seconds
    fn timeout(&self) -> u64;
}
```

#### Task 3: Refactor Rust Implementation (2 hours)
Move existing Rust code into new architecture:
- Extract from `rust_tree_sitter_mutations.rs` → `operators/rust.rs`
- Extract from `rust_adapter.rs` → `adapters/rust.rs`
- Implement `MutationOperator` and `TestAdapter` traits

#### Task 4: Implement Python Mutation Operators (4 hours)
**File**: `server/src/services/mutation/operators/python.rs`

**Mutation Operators** (5 operators for Day 1):
1. **Binary Operators**: `+` ↔ `-`, `*` ↔ `/`, `//` ↔ `%`
2. **Comparison Operators**: `>` ↔ `<`, `>=` ↔ `<=`, `==` ↔ `!=`
3. **Boolean Operators**: `and` ↔ `or`, `not` removed
4. **Return Values**: `True` ↔ `False`, `0` ↔ `1`
5. **String Mutations**: `""` ↔ `"<MUTANT>"`, string concatenation

**Implementation**:
```rust
use super::MutationOperator;
use crate::services::mutation::types::Mutant;
use std::path::Path;
use tree_sitter::{Parser, Query, QueryCursor};

pub struct PythonMutationOperator {
    parser: Parser,
}

impl PythonMutationOperator {
    pub fn new() -> Result<Self, String> {
        let mut parser = Parser::new();
        parser
            .set_language(tree_sitter_python::language())
            .map_err(|e| format!("Failed to set Python parser: {}", e))?;
        Ok(Self { parser })
    }
}

impl MutationOperator for PythonMutationOperator {
    fn generate_mutants(&self, source: &str, file_path: &Path) -> Result<Vec<Mutant>, String> {
        let tree = self.parser.parse(source, None)
            .ok_or("Failed to parse Python source")?;

        let mut mutants = Vec::new();

        // Binary operators
        let binary_query = Query::new(
            tree_sitter_python::language(),
            "(binary_operator left: (_) operator: _ @op right: (_))"
        ).map_err(|e| format!("Failed to create query: {}", e))?;

        let mut cursor = QueryCursor::new();
        for m in cursor.matches(&binary_query, tree.root_node(), source.as_bytes()) {
            for capture in m.captures {
                let op_text = capture.node.utf8_text(source.as_bytes()).unwrap();
                let replacement = match op_text {
                    "+" => "-",
                    "-" => "+",
                    "*" => "/",
                    "/" => "*",
                    "//" => "%",
                    _ => continue,
                };

                mutants.push(Mutant {
                    original_file: file_path.to_path_buf(),
                    location: (
                        capture.node.start_position().row + 1,
                        capture.node.start_position().column + 1,
                        capture.node.end_position().row + 1,
                        capture.node.end_position().column + 1,
                    ),
                    operator: format!("BinaryOp({} → {})", op_text, replacement),
                    original_source: op_text.to_string(),
                    mutated_source: replacement.to_string(),
                });
            }
        }

        Ok(mutants)
    }

    fn apply_mutant(&self, source: &str, mutant: &Mutant) -> Result<String, String> {
        // Apply byte-level replacement (same logic as Rust)
        let bytes = source.as_bytes();
        let start_byte = /* calculate from location */;
        let end_byte = /* calculate from location */;

        let mut mutated = Vec::new();
        mutated.extend_from_slice(&bytes[..start_byte]);
        mutated.extend_from_slice(mutant.mutated_source.as_bytes());
        mutated.extend_from_slice(&bytes[end_byte..]);

        String::from_utf8(mutated).map_err(|e| format!("Invalid UTF-8: {}", e))
    }
}
```

#### Task 5: Implement Python Test Adapter (2 hours)
**File**: `server/src/services/mutation/adapters/python.rs`

```rust
use super::TestAdapter;
use crate::services::mutation::types::MutantStatus;
use std::path::Path;
use std::process::Command;
use std::time::Duration;

pub struct PythonTestAdapter {
    timeout: u64,
}

impl PythonTestAdapter {
    pub fn new(timeout: u64) -> Self {
        Self { timeout }
    }
}

impl TestAdapter for PythonTestAdapter {
    fn run_tests(&self, mutated_source: &str, original_file: &Path) -> Result<MutantStatus, String> {
        // Write mutated source to temporary file
        let temp_file = format!("/tmp/mutant_{}.py", uuid::Uuid::new_v4());
        std::fs::write(&temp_file, mutated_source)
            .map_err(|e| format!("Failed to write temp file: {}", e))?;

        // Run pytest
        let output = Command::new("pytest")
            .arg(&temp_file)
            .arg("--tb=short")
            .arg("-q")
            .timeout(Duration::from_secs(self.timeout))
            .output()
            .map_err(|e| format!("Failed to run pytest: {}", e))?;

        // Clean up
        let _ = std::fs::remove_file(&temp_file);

        // Determine status
        if output.status.success() {
            Ok(MutantStatus::Survived)
        } else if output.status.code() == Some(1) {
            Ok(MutantStatus::Killed)
        } else {
            Ok(MutantStatus::CompileError)
        }
    }

    fn timeout(&self) -> u64 {
        self.timeout
    }
}
```

#### Task 6: Update Engine to Support Multiple Languages (1 hour)
**File**: `server/src/services/mutation/engine.rs`

```rust
use crate::services::mutation::language_detector::{Language, LanguageDetector};
use crate::services::mutation::operators::{MutationOperator, rust::RustMutationOperator, python::PythonMutationOperator};
use crate::services::mutation::adapters::{TestAdapter, rust::RustTestAdapter, python::PythonTestAdapter};

pub struct MutationEngine {
    language: Language,
    operator: Box<dyn MutationOperator>,
    adapter: Box<dyn TestAdapter>,
}

impl MutationEngine {
    pub fn new(file_path: &Path, timeout: u64) -> Result<Self, String> {
        let language = Language::from_extension(file_path);

        let (operator, adapter): (Box<dyn MutationOperator>, Box<dyn TestAdapter>) = match language {
            Language::Rust => (
                Box::new(RustMutationOperator::new()?),
                Box::new(RustTestAdapter::new(timeout)),
            ),
            Language::Python => (
                Box::new(PythonMutationOperator::new()?),
                Box::new(PythonTestAdapter::new(timeout)),
            ),
            _ => return Err(format!("Unsupported language: {:?}", language)),
        };

        Ok(Self { language, operator, adapter })
    }

    pub fn generate_mutants(&self, source: &str, file_path: &Path) -> Result<Vec<Mutant>, String> {
        self.operator.generate_mutants(source, file_path)
    }

    pub fn test_mutant(&self, source: &str, mutant: &Mutant) -> Result<MutantStatus, String> {
        let mutated_source = self.operator.apply_mutant(source, mutant)?;
        self.adapter.run_tests(&mutated_source, &mutant.original_file)
    }
}
```

#### Task 7: Add Integration Tests (1 hour)
**File**: `server/tests/mutation_multi_language_tests.rs`

```rust
#[test]
fn test_python_mutation_generation() {
    let python_code = r#"
def add(a, b):
    return a + b

def is_positive(x):
    return x > 0
"#;

    let temp_file = std::env::temp_dir().join("test_python.py");
    std::fs::write(&temp_file, python_code).unwrap();

    let engine = MutationEngine::new(&temp_file, 30).unwrap();
    let mutants = engine.generate_mutants(python_code, &temp_file).unwrap();

    assert!(mutants.len() >= 2); // At least + → - and > → <
    assert!(mutants.iter().any(|m| m.operator.contains("BinaryOp(+ → -)")));
    assert!(mutants.iter().any(|m| m.operator.contains("ComparisonOp(> → <)")));
}

#[test]
fn test_python_test_execution() {
    let python_code = r#"
def divide(a, b):
    if b == 0:
        raise ValueError("Division by zero")
    return a / b

def test_divide():
    assert divide(10, 2) == 5
    assert divide(20, 4) == 5
"#;

    let temp_file = std::env::temp_dir().join("test_python_exec.py");
    std::fs::write(&temp_file, python_code).unwrap();

    let engine = MutationEngine::new(&temp_file, 30).unwrap();
    let mutants = engine.generate_mutants(python_code, &temp_file).unwrap();

    // Test first mutant (likely == → !=)
    let mutant = &mutants[0];
    let status = engine.test_mutant(python_code, mutant).unwrap();
    assert_eq!(status, MutantStatus::Killed); // Should be caught by tests
}
```

---

### Day 2: TypeScript and Go Support

#### Task 1: Implement TypeScript Mutation Operators (4 hours)
**File**: `server/src/services/mutation/operators/typescript.rs`

**Mutation Operators** (8 operators):
1. **Binary Operators**: Same as Rust/Python
2. **Comparison Operators**: Same as Rust/Python
3. **Boolean Operators**: `&&` ↔ `||`, `!` removed
4. **Ternary Operators**: `? :` condition flipped
5. **Template Literals**: Mutate `${var}` interpolation
6. **Arrow Functions**: Mutate return expressions
7. **Type Assertions**: Remove/modify `as Type`
8. **Optional Chaining**: Remove `?.` → `.`

**Dependencies**:
```toml
# Cargo.toml
tree-sitter-typescript = "0.20"  # Add to dependencies
```

#### Task 2: Implement TypeScript Test Adapter (2 hours)
**File**: `server/src/services/mutation/adapters/typescript.rs`

Support multiple test frameworks:
- Jest (default)
- Mocha
- Vitest

Detection logic:
```rust
fn detect_test_framework(project_dir: &Path) -> TestFramework {
    let package_json = project_dir.join("package.json");
    if package_json.exists() {
        let content = std::fs::read_to_string(&package_json).unwrap_or_default();
        if content.contains("\"jest\"") {
            return TestFramework::Jest;
        } else if content.contains("\"mocha\"") {
            return TestFramework::Mocha;
        } else if content.contains("\"vitest\"") {
            return TestFramework::Vitest;
        }
    }
    TestFramework::Jest // Default
}
```

#### Task 3: Implement Go Mutation Operators (4 hours)
**File**: `server/src/services/mutation/operators/go.rs`

**Mutation Operators** (7 operators):
1. **Binary Operators**: Same as other languages
2. **Comparison Operators**: Same as other languages
3. **Boolean Operators**: `&&` ↔ `||`, `!` removed
4. **Slice Operations**: Mutate slice bounds `[:]`, `[1:]`, `[:len]`
5. **Channel Operations**: `<-ch` timing mutations
6. **Goroutines**: Remove `go` keyword (make synchronous)
7. **Defer Statements**: Remove `defer` keyword

**Dependencies**:
```toml
# Cargo.toml
tree-sitter-go = "0.20"  # Add to dependencies
```

#### Task 4: Implement Go Test Adapter (2 hours)
**File**: `server/src/services/mutation/adapters/go.rs`

```rust
impl TestAdapter for GoTestAdapter {
    fn run_tests(&self, mutated_source: &str, original_file: &Path) -> Result<MutantStatus, String> {
        // Write mutated source to temp file
        let temp_file = format!("/tmp/mutant_{}.go", uuid::Uuid::new_v4());
        std::fs::write(&temp_file, mutated_source)
            .map_err(|e| format!("Failed to write temp file: {}", e))?;

        // Run go test
        let output = Command::new("go")
            .arg("test")
            .arg(&temp_file)
            .arg("-v")
            .timeout(Duration::from_secs(self.timeout))
            .output()
            .map_err(|e| format!("Failed to run go test: {}", e))?;

        // Parse output
        let stdout = String::from_utf8_lossy(&output.stdout);
        if stdout.contains("PASS") {
            Ok(MutantStatus::Survived)
        } else if stdout.contains("FAIL") {
            Ok(MutantStatus::Killed)
        } else {
            Ok(MutantStatus::CompileError)
        }
    }

    fn timeout(&self) -> u64 {
        self.timeout
    }
}
```

#### Task 5: Integration Tests for TypeScript and Go (2 hours)
Add comprehensive test coverage for both languages

---

### Day 3: C++ Support, Documentation, and Release

#### Task 1: Implement C++ Mutation Operators (4 hours)
**File**: `server/src/services/mutation/operators/cpp.rs`

**Mutation Operators** (8 operators):
1. **Binary Operators**: Same as other languages
2. **Comparison Operators**: Same as other languages
3. **Boolean Operators**: `&&` ↔ `||`, `!` removed
4. **Pointer Operations**: `*ptr` ↔ `ptr`, `&var` removed
5. **Increment/Decrement**: `++` ↔ `--`, `+=` ↔ `-=`
6. **Member Access**: `.` ↔ `->`
7. **Template Arguments**: Mutate template parameters
8. **Move Semantics**: `std::move()` removed

**Dependencies**:
```toml
# Cargo.toml
tree-sitter-cpp = "0.20"  # Add to dependencies
```

#### Task 2: Implement C++ Test Adapter (2 hours)
**File**: `server/src/services/mutation/adapters/cpp.rs`

Support multiple test frameworks:
- Google Test (gtest) - default
- Catch2
- Boost.Test

Detection logic similar to TypeScript (check CMakeLists.txt or Makefile)

#### Task 3: Update CLI Handler (1 hour)
**File**: `server/src/cli/handlers/mutate.rs`

Update to show language information:
```rust
println!("Detected language: {}", language.name());
println!("Mutation operators: {} loaded", operator_count);
```

#### Task 4: Update Documentation (2 hours)

**Update files**:
1. `server/README.md` - Add multi-language examples
2. `CHANGELOG.md` - Add v2.176.0 release notes
3. `pmat-book/src/ch28-00-mutation-testing.md` - Add language-specific sections
4. `docs/execution/SPRINT-63-PROGRESS.md` - Track implementation status

**Example additions to Chapter 28**:
```markdown
## Multi-Language Support (v2.176.0+)

### Python Mutation Testing

\`\`\`bash
# Mutate Python file
pmat mutate --target src/calculator.py

# With pytest
pmat mutate --target tests/test_math.py --timeout 30
\`\`\`

### TypeScript Mutation Testing

\`\`\`bash
# Mutate TypeScript file (auto-detects Jest/Mocha)
pmat mutate --target src/utils.ts

# React component mutation
pmat mutate --target src/components/Button.tsx
\`\`\`

### Go Mutation Testing

\`\`\`bash
# Mutate Go file
pmat mutate --target pkg/calculator.go

# Test package
pmat mutate --target pkg/ --timeout 60
\`\`\`

### C++ Mutation Testing

\`\`\`bash
# Mutate C++ file (auto-detects gtest/Catch2)
pmat mutate --target src/calculator.cpp

# Header file mutation
pmat mutate --target include/utils.hpp
\`\`\`
```

#### Task 5: Integration Tests and Quality Gates (2 hours)
```bash
# Run all mutation tests
cargo test --test mutation_multi_language_tests

# Verify language detection
cargo test --lib mutation::language_detector

# Run clippy
cargo clippy --all-targets --all-features

# Build release binary
cargo build --release --bin pmat
```

#### Task 6: Version Bump and Release (1 hour)
```bash
# Update version 2.175.0 → 2.176.0
# Update CHANGELOG.md
# Commit, tag, and push
git commit -m "feat: Add multi-language mutation testing support (Python, TypeScript, Go, C++)"
git tag -a v2.176.0 -m "v2.176.0: Multi-language mutation testing"
git push && git push --tags

# Publish to crates.io
cd server && cargo publish
```

---

## Dependencies

### Rust Crates (Add to `server/Cargo.toml`)
```toml
[dependencies]
tree-sitter = "0.20"
tree-sitter-rust = "0.20"
tree-sitter-python = "0.20"       # NEW
tree-sitter-typescript = "0.20"   # NEW
tree-sitter-go = "0.20"           # NEW
tree-sitter-cpp = "0.20"          # NEW
uuid = { version = "1.0", features = ["v4"] }  # For temp files
```

### External Tools (System Requirements)
Users must have these installed for respective languages:
- **Python**: `pytest` or `unittest`
- **TypeScript**: `npm`, `jest`, or `mocha`
- **Go**: `go` toolchain
- **C++**: `g++`, `cmake`, `gtest` or `catch2`

**Detection Logic**: Warn user if tools are missing
```rust
fn check_prerequisites(language: Language) -> Result<(), String> {
    match language {
        Language::Python => {
            Command::new("pytest").arg("--version").status()
                .map_err(|_| "pytest not found. Install with: pip install pytest")?;
        },
        Language::TypeScript => {
            Command::new("npm").arg("--version").status()
                .map_err(|_| "npm not found. Install Node.js from: https://nodejs.org")?;
        },
        // ... etc
    }
    Ok(())
}
```

---

## Testing Strategy

### Unit Tests (30 tests)
- Language detection (5 tests)
- Operator trait implementations (10 tests per language = 50 tests)
- Adapter trait implementations (10 tests per language = 50 tests)
- **Total**: ~100 unit tests

### Integration Tests (20 tests)
- End-to-end mutation testing per language (4 tests per language = 20 tests)
- Multi-file projects (5 tests)
- Error handling (5 tests)
- **Total**: ~30 integration tests

### Property-Based Tests (10 tests)
- Mutant generation properties (all languages)
- Test adapter properties (all languages)
- Language detection properties

### Manual Testing
Test on real-world projects:
- **Rust**: `pmat` itself (server/src)
- **Python**: `paiml` packages
- **TypeScript**: Interactive platform (if available)
- **Go**: Any internal Go projects
- **C++**: `paiml-mcp-agent-toolkit` C++ examples

---

## Performance Targets

| Metric | Target | Measurement |
|--------|--------|-------------|
| **Mutant Generation** | <100ms per file | Time to parse and generate mutants |
| **Test Execution** | <30s per mutant | Default timeout, configurable |
| **Memory Usage** | <500MB total | Peak RSS during execution |
| **Throughput** | >10 mutants/sec | Parallel execution efficiency |

**Benchmark Script**:
```bash
#!/bin/bash
# Sprint 63 performance benchmark

echo "=== Multi-Language Performance Benchmark ==="

for lang in rust python typescript go cpp; do
    echo ""
    echo "Testing $lang..."
    time pmat mutate --target examples/$lang/sample.$lang --timeout 30
done
```

---

## Risk Mitigation

### Risk 1: Tree-Sitter Parser Compatibility
**Mitigation**: Use well-maintained tree-sitter grammars with stable APIs
**Fallback**: Implement basic regex-based mutation if parser fails

### Risk 2: Test Framework Detection Failures
**Mitigation**: Support multiple frameworks per language with auto-detection
**Fallback**: Allow users to specify test command manually: `--test-command "pytest {}"`

### Risk 3: Timeout Handling Across Languages
**Mitigation**: Use Rust's `std::process::Command` timeout consistently
**Fallback**: OS-level timeout as last resort

### Risk 4: Temporary File Management
**Mitigation**: Use `uuid` for unique temp files, clean up in `Drop` trait
**Fallback**: Log temp file paths for manual cleanup if needed

---

## Documentation Checklist

- [ ] Update `server/README.md` with multi-language examples
- [ ] Update `pmat-book/src/ch28-00-mutation-testing.md` with language sections
- [ ] Add `docs/guides/mutation-testing-python.md`
- [ ] Add `docs/guides/mutation-testing-typescript.md`
- [ ] Add `docs/guides/mutation-testing-go.md`
- [ ] Add `docs/guides/mutation-testing-cpp.md`
- [ ] Update `CHANGELOG.md` with v2.176.0 notes
- [ ] Update `docs/execution/SPRINT-63-PROGRESS.md` daily
- [ ] Create `examples/` directory with sample projects per language

---

## Success Metrics

### Day 1 Success
- ✅ Python mutation operators implemented (5 operators)
- ✅ Python test adapter working with pytest
- ✅ At least 10 unit tests passing
- ✅ 1 end-to-end Python integration test passing

### Day 2 Success
- ✅ TypeScript mutation operators implemented (8 operators)
- ✅ Go mutation operators implemented (7 operators)
- ✅ Both test adapters working
- ✅ 20+ unit tests passing
- ✅ 2 end-to-end integration tests passing (TS + Go)

### Day 3 Success
- ✅ C++ mutation operators implemented (8 operators)
- ✅ C++ test adapter working with gtest
- ✅ All 5 languages fully tested
- ✅ Documentation complete
- ✅ v2.176.0 released to crates.io and GitHub

### Sprint 63 Success (Overall)
- ✅ 5 languages supported (Rust, Python, TypeScript, Go, C++)
- ✅ 100+ unit tests passing
- ✅ 30+ integration tests passing
- ✅ Performance targets met
- ✅ Documentation complete
- ✅ v2.176.0 released and published

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## Follow-Up Work (Sprint 64+)

### Sprint 64: Advanced Mutation Testing
- Incremental mutation testing (only changed files)
- Mutation caching (skip equivalent mutants)
- Mutation score trending over time
- Badge generation for READMEs

### Sprint 65: IDE Integration
- VS Code extension for inline mutation indicators
- IntelliJ plugin
- Real-time mutation score display

### Future Enhancements
- Java mutation testing (JUnit)
- Ruby mutation testing (RSpec)
- PHP mutation testing (PHPUnit)
- Swift mutation testing (XCTest)

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## References

### Related Sprints
- **Sprint 61**: Mutation Testing CLI Implementation (v2.174.0)
- **Sprint 62**: Output Refinement and Testing (v2.175.0)
- **Sprint 64**: Advanced Features (v2.177.0)

### Existing Code References
- `server/src/services/mutation/engine.rs:1-250` - Current engine
- `server/src/services/mutation/types.rs:1-100` - Mutant types
- `server/src/services/mutation/rust_tree_sitter_mutations.rs:1-400` - Rust operators
- `server/src/cli/handlers/mutate.rs:1-280` - CLI handler

### External Tools
- **Tree-Sitter**: https://tree-sitter.github.io/tree-sitter/
- **cargo-mutants**: https://github.com/sourcefrog/cargo-mutants (reference implementation)
- **mutation-testing.io**: https://mutation-testing.io (industry standards)

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**Document Version**: 1.0
**Last Updated**: October 27, 2025
**Status**: DRAFT - Ready for Sprint 63 kickoff after Sprint 62 completion
