Make BeSameAs and NotBeSameAs handle nulls

cmeeren · Jul 25, 2023 · b8300a8 · b8300a8
1 parent f52d017
commit b8300a8
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Showing 2 changed files with 62 additions and 38 deletions.
diff --git a/src/Faqt.Tests/BasicAssertions.fs b/src/Faqt.Tests/BasicAssertions.fs
@@ -255,13 +255,13 @@ module BeSameAs =
 
 
     [<Fact>]
-    let ``Throws ArgumentNullException for null argument`` () =
-        Assert.Throws<ArgumentNullException>(fun () -> "a".Should().BeSameAs(null) |> ignore)
+    let ``Passes if both subject and expected are null references`` () =
+        (null: string).Should().BeSameAs(null).Id<And<string>>().And.BeNull()
 
 
     [<Fact>]
-    let ``Fails with expected message for null`` () =
-        let x = null
+    let ``Fails with expected message if only subject is null`` () =
+        let x: string = null
         let y = "asd"
 
         fun () -> x.Should().BeSameAs(y)
@@ -276,6 +276,23 @@ null
 """
 
 
+    [<Fact>]
+    let ``Fails with expected message if only expected is null`` () =
+        let x = "asd"
+        let y: string = null
+
+        fun () -> x.Should().BeSameAs(y)
+        |> assertExnMsg
+            $"""
+x
+    should be reference equal to
+null
+    but was
+%i{LanguagePrimitives.PhysicalHash x} System.String
+"asd"
+"""
+
+
     [<Fact>]
     let ``Fails with expected message for non-reference-equal values of generic type even if they are equal`` () =
         let x = Map.empty.Add("a", 1)
@@ -322,13 +339,25 @@ module NotBeSameAs =
 
 
     [<Fact>]
-    let ``Passes for null`` () =
-        null.Should().NotBeSameAs("foo").Id<And<string>>()
+    let ``Passes if only subject is null reference`` () = null.Should().NotBeSameAs("asd")
 
 
     [<Fact>]
-    let ``Throws ArgumentNullException for null argument`` () =
-        Assert.Throws<ArgumentNullException>(fun () -> "a".Should().NotBeSameAs(null) |> ignore)
+    let ``Passes if only expected is null reference`` () = "asd".Should().NotBeSameAs(null)
+
+
+    [<Fact>]
+    let ``Fails with expected message if both subject and expected are null references`` () =
+        fun () ->
+            let x = null
+            x.Should().NotBeSameAs(null)
+        |> assertExnMsg
+            """
+x
+    should not be reference equal to
+null
+    but was the same reference.
+"""
 
 
     [<Fact>]

diff --git a/src/Faqt/BasicAssertions.fs b/src/Faqt/BasicAssertions.fs
@@ -1,6 +1,5 @@
 namespace Faqt
 
-open System
 open System.Runtime.CompilerServices
 open AssertionHelpers
 open Formatting
@@ -65,28 +64,26 @@ type BasicAssertions =
     /// Asserts that the subject is reference equal to the specified value (which must not be null).
     [<Extension>]
     static member BeSameAs(t: Testable<'a>, expected: 'a, ?because) : And<'a> =
-        if isNull (box expected) then
-            raise <| ArgumentNullException(nameof expected)
-
         use _ = t.Assert()
 
-        if isNull (box t.Subject) then
-            t.Fail(
-                "{subject}\n\tshould be reference equal to\n{0} {1}\n{2}\n\t{because}but was\nnull",
-                because,
-                (LanguagePrimitives.PhysicalHash expected).ToString(),
-                typeof<'a>.AssertionName,
-                format expected
-            )
-        elif not (LanguagePrimitives.PhysicalEquality t.Subject expected) then
+        if not (LanguagePrimitives.PhysicalEquality t.Subject expected) then
+            let expectedStr =
+                if isNull (box expected) then
+                    "null"
+                else
+                    $"%i{LanguagePrimitives.PhysicalHash expected} %s{expected.GetType().AssertionName}\n%s{format expected}"
+
+            let actualStr =
+                if isNull (box t.Subject) then
+                    "null"
+                else
+                    $"%i{LanguagePrimitives.PhysicalHash t.Subject} %s{t.Subject.GetType().AssertionName}\n%s{format t.Subject}"
+
             t.Fail(
-                "{subject}\n\tshould be reference equal to\n{0} {1}\n{2}\n\t{because}but was\n{3} {4}\n{actual}",
+                "{subject}\n\tshould be reference equal to\n{0}\n\t{because}but was\n{1}",
                 because,
-                (LanguagePrimitives.PhysicalHash expected).ToString(),
-                typeof<'a>.AssertionName,
-                format expected,
-                (LanguagePrimitives.PhysicalHash t.Subject).ToString(),
-                t.Subject.GetType().AssertionName
+                expectedStr,
+                actualStr
             )
 
         And(t)
@@ -95,21 +92,19 @@ type BasicAssertions =
     /// Asserts that the subject is not reference equal to the specified value (which must not be null).
     [<Extension>]
     static member NotBeSameAs(t: Testable<'a>, expected: 'a, ?because) : And<'a> =
-        if isNull (box expected) then
-            raise <| ArgumentNullException(nameof expected)
-
         use _ = t.Assert()
 
-        if
-            not (isNull (box t.Subject))
-            && LanguagePrimitives.PhysicalEquality t.Subject expected
-        then
+        if LanguagePrimitives.PhysicalEquality t.Subject expected then
+            let expectedStr =
+                if isNull (box expected) then
+                    "null"
+                else
+                    $"%i{LanguagePrimitives.PhysicalHash expected} %s{expected.GetType().AssertionName}\n%s{format expected}"
+
             t.Fail(
-                "{subject}\n\tshould not be reference equal to\n{0} {1}\n{2}\n\t{because}but was the same reference.",
+                "{subject}\n\tshould not be reference equal to\n{0}\n\t{because}but was the same reference.",
                 because,
-                (LanguagePrimitives.PhysicalHash expected).ToString(),
-                typeof<'a>.AssertionName,
-                format expected
+                expectedStr
             )
 
         And(t)