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Add thread safety unit test for LazyCache #318

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Add thread safety unit test for LazyCache #318

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c6efca5
Add thread safety unit test for LazyCache
PetrGuan May 12, 2022
33184d4
Update LazyCacheTests.swift
PetrGuan May 12, 2022
2e5b0c1
Pass dispatchGroup to DispatchQueue instead
PetrGuan Jun 15, 2022
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44 changes: 32 additions & 12 deletions Tests/TSCBasicTests/LazyCacheTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -13,20 +13,19 @@ import XCTest
import TSCBasic

class LazyCacheTests: XCTestCase {
func testBasics() {
class Foo {
var numCalls = 0

var bar: Int { return barCache.getValue(self) }
var barCache = LazyCache<Foo, Int>(someExpensiveMethod)
func someExpensiveMethod() -> Int {
numCalls += 1
return 42
}

private class Foo {
var numCalls = 0

var bar: Int { return barCache.getValue(self) }
var barCache = LazyCache<Foo, Int>(someExpensiveMethod)
func someExpensiveMethod() -> Int {
numCalls += 1
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is this thread safe?

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Yeah I think so. The someExpensiveMethod() is protected by a lock. Maybe LazyCache should be named something like ThreadSafeLazyCache?

return 42
}

// FIXME: Make this a more interesting test once we have concurrency primitives.
}

func testBasics() {
for _ in 0..<10 {
let foo = Foo()
XCTAssertEqual(foo.numCalls, 0)
Expand All @@ -36,4 +35,25 @@ class LazyCacheTests: XCTestCase {
}
}
}

func testThreadSafety() {
let dispatchGroup = DispatchGroup()
let exp = expectation(description: "multi thread")

for _ in 0..<10 {
let foo = Foo()
for _ in 0..<10 {
DispatchQueue.global().async(group: dispatchGroup) {
XCTAssertEqual(foo.bar, 42)
XCTAssertEqual(foo.numCalls, 1)
}
}
}

dispatchGroup.notify(queue: .main) {
exp.fulfill()
}

wait(for: [exp], timeout: 0.2)
}
}