Add a test for assertAll callstacks.

This test can be useful if we ever refactor code and don't
realize we broke our logic for determining how callstacks
are collected.

src/commonTest/kotlin/com/varabyte/truthish/AssertAllTest.kt

@@ -101,4 +101,54 @@ class AssertAllTest {
             }
         }
     }
+
+    @Test
+    fun assertAllCallstacksAreCorrect() {
+        // This test can be useful if we ever refactor code and don't realize we broke our logic for determining how
+        // callstacks are collected.
+
+        val a = "A"
+        val b = "B"
+        val c = "C"
+
+        assertThrows<MultipleReportsError> {
+            assertAll {
+                that(a).isEqualTo(a) // ✅
+                that(a).isEqualTo(b) // ❌   // First failure, line0
+                that(b).isEqualTo(b) // ✅
+                that(b).isEqualTo(c) // ❌   // Second failure, line0 + 2
+                that(c).isEqualTo(a) // ❌   // Third failure, line0 + 3
+                that(c).isEqualTo(c) // ✅
+                that(a).isEqualTo(c) // ❌   // Fourth failure, line0 + 5
+            }
+        }.let { e ->
+            // Use a regex to extract callstack values, so that this test will still pass even if the line numbers change
+            // Example callstack entry: com.varabyte.truthish.AssertAllTest$assertAllCallstacksAreCorrect$2$1.invoke(AssertAllTest.kt:123)
+            val expectedAt = Regex(
+                """com\.varabyte\.truthish\.AssertAllTest${"\\$"}assertAllCallstacksAreCorrect${"\\$"}(\d+)${"\\$"}(\d+)\.invoke\(AssertAllTest\.kt:(\d+)\)"""
+            )
+            val match = expectedAt.matchEntire(e.reports[0].details.find(DetailsFor.AT).toString())!!
+            val outerLambdaId = match.groupValues[1].toInt() // assertThrows
+            val innerLambdaId = match.groupValues[2].toInt() // assertAll
+            val lineNumber = match.groupValues[3].toInt()
+
+            assertAll {
+                // "Error report" to "delta distance from the first report"
+                val reportsToCheck = listOf(
+                    e.reports[1] to 2,
+                    e.reports[2] to 3,
+                    e.reports[3] to 5
+                )
+
+                reportsToCheck.forEach { (report, lineDelta) ->
+                    with(expectedAt.matchEntire(report.details.find(DetailsFor.AT).toString())!!) {
+                        that(groupValues[1].toInt()).isEqualTo(outerLambdaId)
+                        that(groupValues[2].toInt()).isEqualTo(innerLambdaId)
+                        that(groupValues[3].toInt()).isEqualTo(lineNumber + lineDelta)
+                    }
+                }
+            }
+        }
+    }
+
 }