Build and Test

Name: Build And Test
Rating: 92
Author: briannadoubt

Build Swift packages and Xcode projects, run tests, and interpret results.

When to Use

•Building a project to check for errors
•Running unit tests
•Checking code coverage
•Debugging build failures

Quick Start

Swift Package Manager

bash

# Build (debug)
swift build

# Build (release)
swift build -c release

# Build specific target
swift build --target MyTarget

# Build with verbose output
swift build -v

Run Tests

bash

# Run all tests
swift test

# Run specific test class
swift test --filter MyTests

# Run specific test method
swift test --filter MyTests/testSomething

# Run with verbose output (see each test)
swift test -v

# Run tests in parallel
swift test --parallel

Code Coverage

bash

# Enable coverage
swift test --enable-code-coverage

# Find coverage data
COVERAGE_PATH=$(swift test --enable-code-coverage 2>&1 | grep "llvm-cov" | sed 's/.*export //' | awk '{print $1}')

# View coverage report (requires successful test run first)
xcrun llvm-cov report \
  .build/debug/YourPackagePackageTests.xctest/Contents/MacOS/YourPackagePackageTests \
  -instr-profile=.build/debug/codecov/default.profdata

Xcode Projects

bash

# List available schemes
xcodebuild -list

# Build a scheme
xcodebuild -scheme MyScheme -destination 'platform=iOS Simulator,name=iPhone 16' build

# Run tests
xcodebuild -scheme MyScheme -destination 'platform=iOS Simulator,name=iPhone 16' test

# Build for specific SDK
xcodebuild -scheme MyScheme -sdk iphonesimulator build

# Clean build
xcodebuild -scheme MyScheme clean build

Interpreting Build Errors

Common Patterns

bash

# Extract just errors from build output
swift build 2>&1 | grep -E "error:|warning:"

# Get context around errors
swift build 2>&1 | grep -B2 -A2 "error:"

Error Types

Pattern	Meaning
`cannot find 'X' in scope`	Missing import or typo
`type 'X' has no member 'Y'`	Wrong method/property name
`cannot convert value`	Type mismatch
`missing argument`	Function call missing required param
`ambiguous use of`	Multiple matching overloads

Interpreting Test Failures

bash

# Run tests and capture output
swift test 2>&1 | tee test-output.txt

# Find failures
grep -E "failed|FAIL" test-output.txt

# Get failure details
grep -B5 -A10 "failed" test-output.txt

Test Output Format

code

Test Case '-[ModuleTests.MyTests testExample]' started.
/path/to/file.swift:42: error: -[ModuleTests.MyTests testExample] : XCTAssertEqual failed: ("1") is not equal to ("2")
Test Case '-[ModuleTests.MyTests testExample]' failed (0.001 seconds).

Quick Fixes

"No such module"

bash

# Resolve dependencies first
swift package resolve
swift build

Clean Build

bash

# Swift Package
rm -rf .build && swift build

# Xcode
xcodebuild clean && xcodebuild build -scheme MyScheme

Update Dependencies

bash

swift package update

Run Executables

bash

# Run default executable
swift run

# Run specific product
swift run MyExecutable

# Run with arguments
swift run MyExecutable --arg1 value1

# Run release build
swift run -c release MyExecutable

Tips

•Always run swift build before swift test to get cleaner error output
•Use -v (verbose) when you need to see what's happening
•Filter tests with --filter to speed up iteration
•Check Package.swift for available targets and products

MCP Fallback

For structured output or advanced features:

•swift_build - Returns parsed errors/warnings as JSON
•swift_test - Returns test results with pass/fail counts
•swift_run - Captures stdout/stderr separately