Use resources in unit tests with Swift Package Manager

Question

I\'m trying to use a resource file in unit tests and access it with Bundle.path, but it returns nil.

This call in MyProjectTests.swift returns nil:

Answer 1

A Swift script approach for Swift 5.2 and earlier...

Swift Package Manager (SwiftPM)

It is possible to use resources in unit tests with SwiftPM for both macOS and Linux with some additional setup and custom scripts. Here is a description of one possible approach:

The SwiftPM does not yet provide a mechanism for handling resources. The following is a workable approach for using test resources TestResources/ within a package; and, also provides for a consistent TestScratch/ directory for creating test files if needed.

Setup:

• Add test resources directory TestResources/ in the PackageName/ directory.

• For Xcode use, add test resources to project "Build Phases" for the test bundle target.

  • Project Editor > TARGETS > CxSQLiteFrameworkTests > Build Phases > Copy Files: Destination Resources, + add files

• For command line use, set up Bash aliases which include swift-copy-testresources.swift

• Place an executable version of swift-copy-testresources.swift on an appropriate path which is included $PATH.

  • Ubuntu: nano ~/bin/ swift-copy-testresources.swift

Bash Aliases

macOS: nano .bash_profile

alias swiftbuild='swift-copy-testresources.swift $PWD; swift build -Xswiftc "-target" -Xswiftc "x86_64-apple-macosx10.13";'
alias swifttest='swift-copy-testresources.swift $PWD; swift test -Xswiftc "-target" -Xswiftc "x86_64-apple-macosx10.13";'
alias swiftxcode='swift package generate-xcodeproj --xcconfig-overrides Package.xcconfig; echo "REMINDER: set Xcode build system."'

Ubuntu: nano ~/.profile. Apppend to end. Change /opt/swift/current to where Swift is installed for a given system.

#############
### SWIFT ###
#############
if [ -d "/opt/swift/current/usr/bin" ] ; then
    PATH="/opt/swift/current/usr/bin:$PATH"
fi

alias swiftbuild='swift-copy-testresources.swift $PWD; swift build;'
alias swifttest='swift-copy-testresources.swift $PWD; swift test;'

Script: swift-copy-testresources.sh chmod +x

#!/usr/bin/swift

// FILE: swift-copy-testresources.sh
// verify swift path with "which -a swift"
// macOS: /usr/bin/swift 
// Ubuntu: /opt/swift/current/usr/bin/swift 
import Foundation

func copyTestResources() {
    let argv = ProcessInfo.processInfo.arguments
    // for i in 0..

Test Utility Code

////////////////
// MARK: - Linux
//////////////// 
#if os(Linux)

// /PATH_TO_PACKAGE/PackageName/.build/TestResources
func getTestResourcesUrl() -> URL? {
    guard let packagePath = ProcessInfo.processInfo.environment["PWD"]
        else { return nil }
    let packageUrl = URL(fileURLWithPath: packagePath)
    let testResourcesUrl = packageUrl
        .appendingPathComponent(".build", isDirectory: true)
        .appendingPathComponent("TestResources", isDirectory: true)
    return testResourcesUrl
} 

// /PATH_TO_PACKAGE/PackageName/.build/TestScratch
func getTestScratchUrl() -> URL? {
    guard let packagePath = ProcessInfo.processInfo.environment["PWD"]
        else { return nil }
    let packageUrl = URL(fileURLWithPath: packagePath)
    let testScratchUrl = packageUrl
        .appendingPathComponent(".build")
        .appendingPathComponent("TestScratch")
    return testScratchUrl
}

// /PATH_TO_PACKAGE/PackageName/.build/TestScratch
func resetTestScratch() throws {
    if let testScratchUrl = getTestScratchUrl() {
        let fm = FileManager.default
        do {_ = try fm.removeItem(at: testScratchUrl)} catch {}
        _ = try fm.createDirectory(at: testScratchUrl, withIntermediateDirectories: true)
    }
}

///////////////////
// MARK: - macOS
///////////////////
#elseif os(macOS)

func isXcodeTestEnvironment() -> Bool {
    let arg0 = ProcessInfo.processInfo.arguments[0]
    // Use arg0.hasSuffix("/usr/bin/xctest") for command line environment
    return arg0.hasSuffix("/Xcode/Agents/xctest")
}

// /PATH_TO/PackageName/TestResources
func getTestResourcesUrl() -> URL? {
    let testBundle = Bundle(for: CxSQLiteFrameworkTests.self)
    let testBundleUrl = testBundle.bundleURL
    
    if isXcodeTestEnvironment() { // test via Xcode 
        let testResourcesUrl = testBundleUrl
            .appendingPathComponent("Contents", isDirectory: true)
            .appendingPathComponent("Resources", isDirectory: true)
        return testResourcesUrl            
    }
    else { // test via command line
        guard let packagePath = ProcessInfo.processInfo.environment["PWD"]
            else { return nil }
        let packageUrl = URL(fileURLWithPath: packagePath)
        let testResourcesUrl = packageUrl
            .appendingPathComponent(".build", isDirectory: true)
            .appendingPathComponent("TestResources", isDirectory: true)
        return testResourcesUrl
    }
} 

func getTestScratchUrl() -> URL? {
    let testBundle = Bundle(for: CxSQLiteFrameworkTests.self)
    let testBundleUrl = testBundle.bundleURL
    if isXcodeTestEnvironment() {
        return testBundleUrl
            .deletingLastPathComponent()
            .appendingPathComponent("TestScratch")
    }
    else {
        return testBundleUrl
            .deletingLastPathComponent()
            .deletingLastPathComponent()
            .deletingLastPathComponent()
            .appendingPathComponent("TestScratch")
    }
}

func resetTestScratch() throws {
    if let testScratchUrl = getTestScratchUrl() {
        let fm = FileManager.default
        do {_ = try fm.removeItem(at: testScratchUrl)} catch {}
        _ = try fm.createDirectory(at: testScratchUrl, withIntermediateDirectories: true)
    }
}

#endif

File Locations:

Linux

During the swift build and swift test the process environment variable PWD provides a path the package root …/PackageName. The PackageName/TestResources/ files are copied to $PWD/.buid/TestResources. The TestScratch/ directory, if used during test runtime, is created in $PWD/.buid/TestScratch.

.build/
├── debug -> x86_64-unknown-linux/debug
...
├── TestResources
│   └── SomeTestResource.sql      <-- (copied from TestResources/)
├── TestScratch
│   └── SomeTestProduct.sqlitedb  <-- (created by running tests)
└── x86_64-unknown-linux
    └── debug
        ├── PackageName.build/
        │   └── ...
        ├── PackageNamePackageTests.build
        │   └── ...
        ├── PackageNamePackageTests.swiftdoc
        ├── PackageNamePackageTests.swiftmodule
        ├── PackageNamePackageTests.xctest  <-- executable, not Bundle
        ├── PackageName.swiftdoc
        ├── PackageName.swiftmodule
        ├── PackageNameTests.build
        │   └── ...
        ├── PackageNameTests.swiftdoc
        ├── PackageNameTests.swiftmodule
        └── ModuleCache ...

macOS CLI

.build/
|-- TestResources/
|   `-- SomeTestResource.sql      <-- (copied from TestResources/)
|-- TestScratch/
|   `-- SomeTestProduct.sqlitedb  <-- (created by running tests)
...
|-- debug -> x86_64-apple-macosx10.10/debug
`-- x86_64-apple-macosx10.10
    `-- debug
        |-- PackageName.build/
        |-- PackageName.swiftdoc
        |-- PackageName.swiftmodule
        |-- PackageNamePackageTests.xctest
        |   `-- Contents
        |       `-- MacOS
        |           |-- PackageNamePackageTests
        |           `-- PackageNamePackageTests.dSYM
        ...
        `-- libPackageName.a

macOS Xcode

PackageName/TestResources/ files are copied into the test bundle Contents/Resources folder as part of the Build Phases. If used during tests, TestScratch/ is placed alongside the *xctest bundle.

Build/Products/Debug/
|-- PackageNameTests.xctest/
|   `-- Contents/
|       |-- Frameworks/
|       |   |-- ...
|       |   `-- libswift*.dylib
|       |-- Info.plist
|       |-- MacOS/
|       |   `-- PackageNameTests
|       `-- Resources/               <-- (aka TestResources/)
|           |-- SomeTestResource.sql <-- (copied from TestResources/)
|           `-- libswiftRemoteMirror.dylib
`-- TestScratch/
    `-- SomeTestProduct.sqlitedb     <-- (created by running tests)

I also posted a GitHubGist of this same approach at 004.4'2 SW Dev Swift Package Manager (SPM) With Resources Qref