Merge pull request fsprojects#3232 from fsprojects/repo-assist/fix-issue-1740-idempotency-regression-test-b15031aa78b105e3

[Repo Assist] Regression test for idempotency bug with NUnit Assert.That lambda (fsprojects#1740)

Author: nojaf

CHANGELOG.md

@@ -13,6 +13,7 @@
 - Type app closing angle bracket padded by previous expression length. [#3179](https://github.com/fsprojects/fantomas/issues/3179)
 - Dynamic operator on result of qualified function call causes formatting error. [#3135](https://github.com/fsprojects/fantomas/issues/3135)
 - Long delegate type with generic args no longer breaks around arrow. [#2468](https://github.com/fsprojects/fantomas/issues/2468)
+- Idempotency problem when formatting NUnit Assert.That with lambda argument. [#1740](https://github.com/fsprojects/fantomas/issues/1740)
 
 ## [8.0.0-alpha-002] - 2025-12-15
 

src/Fantomas.Core.Tests/AppTests.fs

@@ -1183,3 +1183,24 @@ let ``don't indent function application arguments when function name is further
     b
     c))))))))))))))))))))))
 """
+
+[<Test>]
+let ``idempotency problem when formatting NUnit Assert.That with lambda, 1740`` () =
+    formatSourceString
+        """
+Assert.That(
+    Assert.Throws(fun () -> FooFooFooFooFooFoo.BarBar.dodododo filesfiles [] outoutout |> ignore)
+        .Message,
+    Is.EqualTo(message)
+)
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+Assert.That(
+    Assert.Throws(fun () -> FooFooFooFooFooFoo.BarBar.dodododo filesfiles [] outoutout |> ignore).Message,
+    Is.EqualTo(message)
+)
+"""