Testing async code in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an async function.

Swift

func fetchData() async [1] String {
    return "Data" 
}

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A->

Bthrows

Cawait

Dasync

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'async' instead of '->' to specify return type

Using 'throws' when not throwing errors

The arrow -> is used to specify the return type of the function.

2fill in blank

medium

Complete the code to call an async function with await.

Swift

Task {
    let result = try? await [1]()
    print(result ?? "No data")
}

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AfetchData

BfetchData()

Cawait fetchData

DTask

Attempts:

3 left

💡 Hint

Common Mistakes

Adding parentheses inside the await expression

Calling Task instead of the function

You call the async function by its name without parentheses inside await.

3fill in blank

hard

Fix the error in the async test function declaration.

Swift

func testFetch() [1] async throws {
    let data = try await fetchData()
    XCTAssertEqual(data, "Data")
}

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Aasync

Bthrows

Casync throws

Doverride

Attempts:

3 left

💡 Hint

Common Mistakes

Marking only async or only throws

Forgetting to mark the test function as async

Test functions that call async throwing functions must be marked async throws.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension filtering async results.

Swift

let filtered = try await Dictionary(uniqueKeysWithValues: results.compactMap { item in
    guard let value = item.value, value [1] 10 else { return nil }
    return (item.key, value[2]2)
})

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A>

B*

C**

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > in the guard

Using ** instead of * for multiplication

The guard checks if value is greater than 10, and the value is multiplied by 2 using *.

5fill in blank

hard

Fill all three blanks to create an async test that awaits and asserts a value.

Swift

func testValue() async throws {
    let value = try await [1]()
    XCTAssertEqual(value, [2])
    XCTAssertTrue(value [3] 0)
}

Drag options to blanks, or click blank then click option'

AfetchData

B"Data"

C>

DfetchNumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using fetchData instead of fetchNumber

Using wrong expected value in XCTAssertEqual

The function fetchNumber() is awaited, the expected value is "Data", and the test checks if value is greater than 0.