I am a developer of a developer of MirrorDiffKit that is a structual diff library. I think MirrorDiffKit is useful for Nimble users on some conditions.
So, can Nimble use MirrorDiffKit internally? How do you feel about it?
The output of verifying structs or classes that have many stored properties with Nimble is hard to read:
expected to equal <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m inserted", key3: "i\'m not changed", key4: "i\'m not changed", key5: "i\'m not changed", key6: "i\'m not changed", key7: "i\'m not changed", key8: "i\'m not changed", key9: "i\'m not changed")>, got <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m deleted", key3: "i\'m not changed", key4: "i\'m not changed", key5: "i\'m not changed", key6: "i\'m not changed", key7: "i\'m not changed", key8: "i\'m not changed", key9: "i\'m not changed")>
In this case, MirrorDiffKit is useful. MirrorDiffKit is a diff library that can output stored property differences between two structs or classes or enums. For example, the following string is an output of MirrorDiffKit when comparing two structs:
struct ExampleEquatable {
key1: "i'm not changed"
- key2: "i'm inserted"
+ key2: "i'm deleted"
}
It can make readable output when comparing two structs or classes or enums that have many properties:
expected to equal <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m inserted", key3: "i\'m not changed", key4: "i\'m not changed", key5: "i\'m not changed", key6: "i\'m not changed", key7: "i\'m not changed", key8: "i\'m not changed", key9: "i\'m not changed")>, got <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m deleted", key3: "i\'m not changed", key4: "i\'m not changed", key5: "i\'m not changed", key6: "i\'m not changed", key7: "i\'m not changed", key8: "i\'m not changed", key9: "i\'m not changed")>
It becomes the following string:
struct ExampleEquatable {
key1: "i'm not changed"
- key2: "i'm inserted"
+ key2: "i'm deleted"
key3: "i'm not changed"
key4: "i'm not changed"
key5: "i'm not changed"
key6: "i'm not changed"
key7: "i'm not changed"
key8: "i'm not changed"
key9: "i'm not changed"
}
And also, it can make readable output when comparing two sequences that have different order:
expected to equal <[i'm not changed, i'm not changed, i'm not changed, i'm not changed, i'm not changed, i'm inserted, i'm not changed]>, got <[i'm not changed, i'm deleted, i'm not changed, i'm not changed, i'm not changed, i'm not changed, i'm not changed]>
It becomes the following string:
[
"i'm not changed"
+ "i'm deleted"
"i'm not changed"
"i'm not changed"
"i'm not changed"
"i'm not changed"
- "i'm inserted"
"i'm not changed"
]
As seen above, MirrorDiffKit can help Nimble.
-
Advantage:
- Readable output for large objects
- Readable output for order changes
-
Disadvantage:
-
Problem about CoreGraphics Objects
Currently MirrorDiffKit is not familiar with CoreGraphics Objects. For example, MirrorDiffKit returns the following broken output when comparing 2 CGSize:
struct CGSize { height: generic Double {}, width: generic Double {} } -
Output via xcpretty can be broken
I note the example output at end of the description.
-
import Quick
import Nimble
import MirrorDiffKit
class TableOfContentsSpec: QuickSpec {
override func spec() {
describe("Comparison for ExampleEquatable") {
context("when not using MirrorDiffKit") {
it("print messy output") {
let a = ExampleEquatable(
key1: "i'm not changed",
key2: "i'm deleted"
)
let b = ExampleEquatable(
key1: "i'm not changed",
key2: "i'm inserted"
)
expect(a).to(equal(b))
}
}
context("when using MirrorDiffKit") {
it("print readable output") {
let a = ExampleEquatable(
key1: "i'm not changed",
key2: "i'm deleted"
)
let b = ExampleEquatable(
key1: "i'm not changed",
key2: "i'm inserted"
)
expect(a).to(equal(b), description: diff(between: b, and: a))
}
}
}
}
struct ExampleEquatable: Equatable {
let key1: String
let key2: String
static func ==(lhs: ExampleEquatable, rhs: ExampleEquatable) -> Bool {
return lhs.key1 == rhs.key1
&& lhs.key2 == rhs.key2
}
}
$ xcodebuild test -scheme QuickPlaygroundTests -destination 'platform=iOS Simulator,name=iPhone X,OS=latest'
Test Suite 'All tests' started at 2017-10-16 22:35:19.748
Test Suite 'QuickPlaygroundTests.xctest' started at 2017-10-16 22:35:19.749
Test Suite 'TableOfContentsSpec' started at 2017-10-16 22:35:19.751
Test Case '-[QuickPlaygroundTests.TableOfContentsSpec ExampleEquatable__when_not_using_MirrorDiffKit__print_messy_output]' started.
/Users/Kuniwak/Development/QuickPlayground/QuickPlaygroundTests/QuickPlaygroundTests.swift:19: error: -[QuickPlaygroundTests.TableOfContentsSpec ExampleEquatable__when_not_using_MirrorDiffKit__print_messy_output] : expected to equal <ExampleEquatable(key1: "i\'m notchanged", key2: "i\'m inserted")>, got <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m deleted")>
Test Case '-[QuickPlaygroundTests.TableOfContentsSpec ExampleEquatable__when_not_using_MirrorDiffKit__print_messy_output]' failed (0.013 seconds).
Test Case '-[QuickPlaygroundTests.TableOfContentsSpec ExampleEquatable__when_using_MirrorDiffKit__print_readable_output]' started.
/Users/Kuniwak/Development/QuickPlayground/QuickPlaygroundTests/QuickPlaygroundTests.swift:33: error: -[QuickPlaygroundTests.TableOfContentsSpec ExampleEquatable__when_using_MirrorDiffKit__print_readable_output] :
struct ExampleEquatable {
key1: "i'm not changed"
- key2: "i'm inserted"
+ key2: "i'm deleted"
}
expected to equal <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m inserted")>, got <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m deleted")>All tests
Test Suite QuickPlaygroundTests.xctest started
TableOfContentsSpec
✗ ExampleEquatable__when_not_using_MirrorDiffKit__print_messy_output, expected to equal <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m inserted")>, got <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m deleted")>
✗ ExampleEquatable__when_using_MirrorDiffKit__print_readable_output,
QuickPlaygroundTests.TableOfContentsSpec
ExampleEquatable__when_not_using_MirrorDiffKit__print_messy_output, expected to equal <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m inserted")>, got <ExampleEquatable(key1: "i\'m not changed", key2: "i\'m deleted")>
/Users/Kuniwak/Development/QuickPlayground/QuickPlaygroundTests/QuickPlaygroundTests.swift:19
'''
)
expect(a).to(equal(b))
}
'''
ExampleEquatable__when_using_MirrorDiffKit__print_readable_output,
/Users/Kuniwak/Development/QuickPlayground/QuickPlaygroundTests/QuickPlaygroundTests.swift:33
'''
)
expect(a).to(equal(b), description: diff(between: b, and: a))
}
'''
Executed 2 tests, with 2 failures (0 unexpected) in 0.013 (0.015) seconds