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[shared_preferences_foundation] Migrate XCTest to Swift Testing #10766

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[shared_preferences_foundation] Migrate XCTest to Swift Testing
jmagman Jan 10, 2026
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#require
jmagman Jan 10, 2026
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jmagman Jan 10, 2026
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Revert CHANGELOG
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236 changes: 118 additions & 118 deletions packages/shared_preferences/shared_preferences_foundation/darwin/Tests/RunnerTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import XCTest
import Testing

@testable import shared_preferences_foundation

Expand All @@ -12,104 +12,104 @@ import XCTest
import FlutterMacOS
#endif

class RunnerTests: XCTestCase {
// The shared preferences API is thread-safe.
// Serially mutate shared preferences
// so tests don't stomp on each other.
@Suite(.serialized)
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@jmagman jmagman Jan 10, 2026

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Lots of test failures when these tests run in parallel. For example, there's no locking in the update methods like:

packages/packages/shared_preferences/shared_preferences_foundation/darwin/shared_preferences_foundation/Sources/shared_preferences_foundation/SharedPreferencesPlugin.swift

Lines 133 to 144 in fb3e908

func clear(allowList: [String]?, options: SharedPreferencesPigeonOptions) throws {
let defaults = try SharedPreferencesPlugin.getUserDefaults(options: options)
if let allowList = allowList {
for (key) in allowList {
defaults.removeObject(forKey: key)
}
} else {
for key in defaults.dictionaryRepresentation().keys {
defaults.removeObject(forKey: key)
}
}
}

Should probably be migrated to actor?

Surprisingly I don't see any open issues that look related.

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@hellohuanlin hellohuanlin Jan 12, 2026

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Should probably be migrated to actor?

We now have toooo many options!

  1. Actor
  2. GCD
  3. the new Synchronization framework introduced last year
  4. Locks (os_unfair_lock is likely the most performant)

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@hellohuanlin hellohuanlin Jan 12, 2026

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Worth adding a TODO to remove .serialized?

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@jmagman jmagman Jan 27, 2026

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Come to think of it, this isn't actually a bug. The defaults themselves are a threadsafe API, so if calling code, like these tests, are relying on another thread not mutating the defaults, then it would up to that calling code to handle it. I actually now think @Suite(.serialized) is correct. I'll add a comment.

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@tarrinneal tarrinneal Jan 27, 2026

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I was going to say something like this. My understanding when I wrote this code is that behavior is expected. I can see changing it though, if we wanted to make the plugin work that way instead.

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@jmagman jmagman Jan 27, 2026 •
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There's still a few pieces here that look a little thread unsafe, for example:

packages/packages/shared_preferences/shared_preferences_foundation/darwin/shared_preferences_foundation/Sources/shared_preferences_foundation/SharedPreferencesPlugin.swift

Lines 140 to 142 in fb3e908

for key in defaults.dictionaryRepresentation().keys {
defaults.removeObject(forKey: key)
}

That's looping over a collection while mutating it, which is generally not a good pattern. There's no guarantee the defaults wouldn't be added by another thread while it's being cleared. correction: no it's not, it's looping over the dictionary representation.
But it's way less dire than I made it out to be in the initial description. Sorry.

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@tarrinneal tarrinneal Jan 27, 2026

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Had me worried there for a second :)

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@tarrinneal tarrinneal Jan 27, 2026

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If there are others, I'd be happy to hear about them though. I'm always happy to learn from my mistakes.

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@jmagman jmagman Jan 27, 2026

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Sorry for the noise and panic, @tarrinneal 🙂

struct RunnerTests {
let testKey = "foo"
let testKeyTwo = "baz"
let testValue = "bar"

// Legacy system tests.

let prefixes: [String] = ["aPrefix", ""]

func testSetAndGet() throws {
for aPrefix in prefixes {
let plugin = LegacySharedPreferencesPlugin()

plugin.setBool(key: "\(aPrefix)aBool", value: true)
plugin.setDouble(key: "\(aPrefix)aDouble", value: 3.14)
plugin.setValue(key: "\(aPrefix)anInt", value: 42)
plugin.setValue(key: "\(aPrefix)aString", value: "hello world")
plugin.setValue(key: "\(aPrefix)aStringList", value: ["hello", "world"])

let storedValues = plugin.getAll(prefix: aPrefix, allowList: nil)
XCTAssertEqual(storedValues["\(aPrefix)aBool"] as? Bool, true)
XCTAssertEqual(storedValues["\(aPrefix)aDouble"] as! Double, 3.14, accuracy: 0.0001)
XCTAssertEqual(storedValues["\(aPrefix)anInt"] as? Int, 42)
XCTAssertEqual(storedValues["\(aPrefix)aString"] as? String, "hello world")
XCTAssertEqual(storedValues["\(aPrefix)aStringList"] as? [String], ["hello", "world"])
}
@Test(arguments: ["aPrefix", ""])
func setAndGet(prefix: String) throws {
let plugin = LegacySharedPreferencesPlugin()

plugin.setBool(key: "\(prefix)aBool", value: true)
plugin.setDouble(key: "\(prefix)aDouble", value: 3.14)
plugin.setValue(key: "\(prefix)anInt", value: 42)
plugin.setValue(key: "\(prefix)aString", value: "hello world")
plugin.setValue(key: "\(prefix)aStringList", value: ["hello", "world"])

let storedValues = plugin.getAll(prefix: prefix, allowList: nil)
#expect(storedValues["\(prefix)aBool"] as? Bool == true)

let doubleValue = try #require(storedValues["\(prefix)aDouble"] as? Double)
#expect(abs(doubleValue - 3.14) < 0.0001)

#expect(storedValues["\(prefix)anInt"] as? Int == 42)
#expect(storedValues["\(prefix)aString"] as? String == "hello world")
#expect(storedValues["\(prefix)aStringList"] as? [String] == ["hello", "world"])
}

func testGetWithAllowList() throws {
for aPrefix in prefixes {
let plugin = LegacySharedPreferencesPlugin()

plugin.setBool(key: "\(aPrefix)aBool", value: true)
plugin.setDouble(key: "\(aPrefix)aDouble", value: 3.14)
plugin.setValue(key: "\(aPrefix)anInt", value: 42)
plugin.setValue(key: "\(aPrefix)aString", value: "hello world")
plugin.setValue(key: "\(aPrefix)aStringList", value: ["hello", "world"])

let storedValues = plugin.getAll(prefix: aPrefix, allowList: ["\(aPrefix)aBool"])
XCTAssertEqual(storedValues["\(aPrefix)aBool"] as? Bool, true)
XCTAssertNil(storedValues["\(aPrefix)aDouble"] ?? nil)
XCTAssertNil(storedValues["\(aPrefix)anInt"] ?? nil)
XCTAssertNil(storedValues["\(aPrefix)aString"] ?? nil)
XCTAssertNil(storedValues["\(aPrefix)aStringList"] ?? nil)
}
@Test(arguments: ["aPrefix", ""])
func getWithAllowList(prefix: String) throws {
let plugin = LegacySharedPreferencesPlugin()

plugin.setBool(key: "\(prefix)aBool", value: true)
plugin.setDouble(key: "\(prefix)aDouble", value: 3.14)
plugin.setValue(key: "\(prefix)anInt", value: 42)
plugin.setValue(key: "\(prefix)aString", value: "hello world")
plugin.setValue(key: "\(prefix)aStringList", value: ["hello", "world"])

let storedValues = plugin.getAll(prefix: prefix, allowList: ["\(prefix)aBool"])
#expect(storedValues["\(prefix)aBool"] as? Bool == true)
#expect(storedValues["\(prefix)aDouble"] == nil)
#expect(storedValues["\(prefix)anInt"] == nil)
#expect(storedValues["\(prefix)aString"] == nil)
#expect(storedValues["\(prefix)aStringList"] == nil)
}

func testRemove() throws {
for aPrefix in prefixes {
let plugin = LegacySharedPreferencesPlugin()
let testKey = "\(aPrefix)\(testKey)"
plugin.setValue(key: testKey, value: 42)
@Test(arguments: ["aPrefix", ""])
func remove(prefix: String) throws {
let plugin = LegacySharedPreferencesPlugin()
let key = "\(prefix)\(testKey)"
plugin.setValue(key: key, value: 42)

// Make sure there is something to remove, so the test can't pass due to a set failure.
let preRemovalValues = plugin.getAll(prefix: aPrefix, allowList: nil)
XCTAssertEqual(preRemovalValues[testKey] as? Int, 42)
// Make sure there is something to remove, so the test can't pass due to a set failure.
let preRemovalValues = plugin.getAll(prefix: prefix, allowList: nil)
#expect(preRemovalValues[key] as? Int == 42)

// Then verify that removing it works.
plugin.remove(key: testKey)
// Then verify that removing it works.
plugin.remove(key: key)

let finalValues = plugin.getAll(prefix: aPrefix, allowList: nil)
XCTAssertNil(finalValues[testKey] as Any?)
}
let finalValues = plugin.getAll(prefix: prefix, allowList: nil)
#expect(finalValues[key] == nil)
}

func testClearWithNoAllowlist() throws {
for aPrefix in prefixes {
let plugin = LegacySharedPreferencesPlugin()
let testKey = "\(aPrefix)\(testKey)"
plugin.setValue(key: testKey, value: 42)
@Test(arguments: ["aPrefix", ""])
func clearWithNoAllowlist(prefix: String) throws {
let plugin = LegacySharedPreferencesPlugin()
let key = "\(prefix)\(testKey)"
plugin.setValue(key: key, value: 42)

// Make sure there is something to clear, so the test can't pass due to a set failure.
let preRemovalValues = plugin.getAll(prefix: aPrefix, allowList: nil)
XCTAssertEqual(preRemovalValues[testKey] as? Int, 42)
// Make sure there is something to clear, so the test can't pass due to a set failure.
let preRemovalValues = plugin.getAll(prefix: prefix, allowList: nil)
#expect(preRemovalValues[key] as? Int == 42)

// Then verify that clearing works.
plugin.clear(prefix: aPrefix, allowList: nil)
// Then verify that clearing works.
#expect(plugin.clear(prefix: prefix, allowList: nil) == true)

let finalValues = plugin.getAll(prefix: aPrefix, allowList: nil)
XCTAssertNil(finalValues[testKey] as Any?)
}
let finalValues = plugin.getAll(prefix: prefix, allowList: nil)
#expect(finalValues[key] == nil)
}

func testClearWithAllowlist() throws {
for aPrefix in prefixes {
let plugin = LegacySharedPreferencesPlugin()
let testKey = "\(aPrefix)\(testKey)"
plugin.setValue(key: testKey, value: 42)
@Test(arguments: ["aPrefix", ""])
func clearWithAllowlist(prefix: String) throws {
let plugin = LegacySharedPreferencesPlugin()
let key = "\(prefix)\(testKey)"
plugin.setValue(key: key, value: 42)

// Make sure there is something to clear, so the test can't pass due to a set failure.
let preRemovalValues = plugin.getAll(prefix: aPrefix, allowList: nil)
XCTAssertEqual(preRemovalValues[testKey] as? Int, 42)
// Make sure there is something to clear, so the test can't pass due to a set failure.
let preRemovalValues = plugin.getAll(prefix: prefix, allowList: nil)
#expect(preRemovalValues[key] as? Int == 42)

plugin.clear(prefix: aPrefix, allowList: ["\(aPrefix)\(testKeyTwo)"])
#expect(plugin.clear(prefix: prefix, allowList: ["\(prefix)\(testKeyTwo)"]) == true)

let finalValues = plugin.getAll(prefix: aPrefix, allowList: nil)
XCTAssertEqual(finalValues[testKey] as? Int, 42)
}
let finalValues = plugin.getAll(prefix: prefix, allowList: nil)
#expect(finalValues[key] as? Int == 42)
}

// Async system tests.
Expand All @@ -118,7 +118,7 @@ class RunnerTests: XCTestCase {
let optionsWithSuiteName = SharedPreferencesPigeonOptions(
suiteName: "group.example.sharedPreferencesFoundationExample")

func testAsyncSetAndGet() throws {
@Test func asyncSetAndGet() throws {
let plugin = SharedPreferencesPlugin()

try plugin.set(key: "aBool", value: true, options: emptyOptions)
Expand All @@ -127,18 +127,19 @@ class RunnerTests: XCTestCase {
try plugin.set(key: "aString", value: "hello world", options: emptyOptions)
try plugin.set(key: "aStringList", value: ["hello", "world"], options: emptyOptions)

XCTAssertEqual(((try plugin.getValue(key: "aBool", options: emptyOptions)) != nil), true)
XCTAssertEqual(
try plugin.getValue(key: "aDouble", options: emptyOptions) as! Double, 3.14, accuracy: 0.0001)
XCTAssertEqual(try plugin.getValue(key: "anInt", options: emptyOptions) as! Int, 42)
XCTAssertEqual(
try plugin.getValue(key: "aString", options: emptyOptions) as! String, "hello world")
XCTAssertEqual(
try plugin.getValue(key: "aStringList", options: emptyOptions) as! [String],
["hello", "world"])
#expect((try plugin.getValue(key: "aBool", options: emptyOptions)) != nil)
let doubleVal = try #require(plugin.getValue(key: "aDouble", options: emptyOptions) as? Double)
#expect(abs(doubleVal - 3.14) < 0.0001)

#expect(try plugin.getValue(key: "anInt", options: emptyOptions) as? Int == 42)
#expect(try plugin.getValue(key: "aString", options: emptyOptions) as? String == "hello world")
#expect(
try plugin.getValue(key: "aStringList", options: emptyOptions) as? [String] == [
"hello", "world",
])
}

func testAsyncGetAll() throws {
@Test func asyncGetAll() throws {
let plugin = SharedPreferencesPlugin()

try plugin.set(key: "aBool", value: true, options: emptyOptions)
Expand All @@ -148,28 +149,30 @@ class RunnerTests: XCTestCase {
try plugin.set(key: "aStringList", value: ["hello", "world"], options: emptyOptions)

let storedValues = try plugin.getAll(allowList: nil, options: emptyOptions)
XCTAssertEqual(storedValues["aBool"] as? Bool, true)
XCTAssertEqual(storedValues["aDouble"] as! Double, 3.14, accuracy: 0.0001)
XCTAssertEqual(storedValues["anInt"] as? Int, 42)
XCTAssertEqual(storedValues["aString"] as? String, "hello world")
XCTAssertEqual(storedValues["aStringList"] as? [String], ["hello", "world"])
#expect(storedValues["aBool"] as? Bool == true)

let doubleVal = try #require(storedValues["aDouble"] as? Double)
#expect(abs(doubleVal - 3.14) < 0.0001)

#expect(storedValues["anInt"] as? Int == 42)
#expect(storedValues["aString"] as? String == "hello world")
#expect(storedValues["aStringList"] as? [String] == ["hello", "world"])
}

func testAsyncGetAllWithAndWithoutSuiteName() throws {
@Test func asyncGetAllWithAndWithoutSuiteName() throws {
let plugin = SharedPreferencesPlugin()

try plugin.set(key: "aKey", value: "hello world", options: emptyOptions)
try plugin.set(key: "aKeySuite", value: "hello world with suite", options: optionsWithSuiteName)

let storedValues = try plugin.getAll(allowList: nil, options: emptyOptions)
XCTAssertEqual(storedValues["aKey"] as? String, "hello world")
#expect(storedValues["aKey"] as? String == "hello world")

let storedValuesWithGroup = try plugin.getAll(allowList: nil, options: optionsWithSuiteName)
XCTAssertEqual(storedValuesWithGroup["aKeySuite"] as? String, "hello world with suite")
#expect(storedValuesWithGroup["aKeySuite"] as? String == "hello world with suite")
}

func testAsyncGetAllWithAllowList() throws {
@Test func asyncGetAllWithAllowList() throws {
let plugin = SharedPreferencesPlugin()

try plugin.set(key: "aBool", value: true, options: emptyOptions)
Expand All @@ -179,61 +182,58 @@ class RunnerTests: XCTestCase {
try plugin.set(key: "aStringList", value: ["hello", "world"], options: emptyOptions)

let storedValues = try plugin.getAll(allowList: ["aBool"], options: emptyOptions)
XCTAssertEqual(storedValues["aBool"] as? Bool, true)
XCTAssertNil(storedValues["aDouble"] ?? nil)
XCTAssertNil(storedValues["anInt"] ?? nil)
XCTAssertNil(storedValues["aString"] ?? nil)
XCTAssertNil(storedValues["aStringList"] ?? nil)

#expect(storedValues["aBool"] as? Bool == true)
#expect(storedValues["aDouble"] == nil)
#expect(storedValues["anInt"] == nil)
#expect(storedValues["aString"] == nil)
#expect(storedValues["aStringList"] == nil)
}

func testAsyncRemove() throws {
@Test func asyncRemove() throws {
let plugin = SharedPreferencesPlugin()
try plugin.set(key: testKey, value: testValue, options: emptyOptions)

// Make sure there is something to remove, so the test can't pass due to a set failure.
let preRemovalValue = try plugin.getValue(key: testKey, options: emptyOptions) as! String
XCTAssertEqual(preRemovalValue, testValue)
let preRemovalValue = try plugin.getValue(key: testKey, options: emptyOptions) as? String
#expect(preRemovalValue == testValue)

// Then verify that removing it works.
try plugin.remove(key: testKey, options: emptyOptions)

let finalValue = try plugin.getValue(key: testKey, options: emptyOptions)
XCTAssertNil(finalValue)

#expect(finalValue == nil)
}

func testAsyncClearWithNoAllowlist() throws {
@Test func asyncClearWithNoAllowlist() throws {
let plugin = SharedPreferencesPlugin()
try plugin.set(key: testKey, value: testValue, options: emptyOptions)

// Make sure there is something to remove, so the test can't pass due to a set failure.
let preRemovalValue = try plugin.getValue(key: testKey, options: emptyOptions) as! String
XCTAssertEqual(preRemovalValue, testValue)
let preRemovalValue = try plugin.getValue(key: testKey, options: emptyOptions) as? String
#expect(preRemovalValue == testValue)

// Then verify that clearing works.
try plugin.clear(allowList: nil, options: emptyOptions)

let finalValue = try plugin.getValue(key: testKey, options: emptyOptions)
XCTAssertNil(finalValue)

#expect(finalValue == nil)
}

func testAsyncClearWithAllowlist() throws {
@Test func asyncClearWithAllowlist() throws {
let plugin = SharedPreferencesPlugin()

try plugin.set(key: testKey, value: testValue, options: emptyOptions)
try plugin.set(key: testKeyTwo, value: testValue, options: emptyOptions)

// Make sure there is something to clear, so the test can't pass due to a set failure.
let preRemovalValue = try plugin.getValue(key: testKey, options: emptyOptions) as! String
XCTAssertEqual(preRemovalValue, testValue)
let preRemovalValue = try plugin.getValue(key: testKey, options: emptyOptions) as? String
#expect(preRemovalValue == testValue)

try plugin.clear(allowList: [testKey], options: emptyOptions)

let finalValueNil = try plugin.getValue(key: testKey, options: emptyOptions)
XCTAssertNil(finalValueNil)
let finalValueNotNil = try plugin.getValue(key: testKeyTwo, options: emptyOptions) as! String
XCTAssertEqual(finalValueNotNil, testValue)
#expect(finalValueNil == nil)
let finalValueNotNil = try plugin.getValue(key: testKeyTwo, options: emptyOptions) as? String
#expect(finalValueNotNil == testValue)
}
}
6 changes: 3 additions & 3 deletions ...ed_preferences/shared_preferences_foundation/example/ios/Runner.xcodeproj/project.pbxproj
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Original file line number Diff line number Diff line change
Expand Up @@ -485,7 +485,7 @@
PRODUCT_NAME = "$(TARGET_NAME)";
SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
SWIFT_OPTIMIZATION_LEVEL = "-Onone";
SWIFT_VERSION = 5.0;
SWIFT_VERSION = 6.0;
TEST_HOST = "$(BUILT_PRODUCTS_DIR)/Runner.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/Runner";
};
name = Debug;
Expand All @@ -501,7 +501,7 @@
MARKETING_VERSION = 1.0;
PRODUCT_BUNDLE_IDENTIFIER = com.example.sharedPreferencesFoundationExample.RunnerTests;
PRODUCT_NAME = "$(TARGET_NAME)";
SWIFT_VERSION = 5.0;
SWIFT_VERSION = 6.0;
TEST_HOST = "$(BUILT_PRODUCTS_DIR)/Runner.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/Runner";
};
name = Release;
Expand All @@ -517,7 +517,7 @@
MARKETING_VERSION = 1.0;
PRODUCT_BUNDLE_IDENTIFIER = com.example.sharedPreferencesFoundationExample.RunnerTests;
PRODUCT_NAME = "$(TARGET_NAME)";
SWIFT_VERSION = 5.0;
SWIFT_VERSION = 6.0;
TEST_HOST = "$(BUILT_PRODUCTS_DIR)/Runner.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/Runner";
};
name = Profile;
Expand Down
Empty file added packages/shared_preferences/shared_preferences_foundation/example/ios/RunnerTests/.gitkeep
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@jmagman jmagman Jan 10, 2026

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Xcode is expecting this directory:
Image

macOS gets away with it because there's a (probably unnecessary) Info.plist in the equivalent directory:
https://github.com/flutter/packages/tree/fb3e9081ca58b1cb3e54b8bd471c57116a72585e/packages/shared_preferences/shared_preferences_foundation/example/macos/RunnerTests

Empty file.
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