Reproduce issue #5504 in scripted test

sbt-app/src/sbt-test/tests/test-quick/changed/MathFunction.scala

@@ -0,0 +1,3 @@
+object MathFunction {
+  def times2(i: Int): Int = 2 * 2
+}

sbt-app/src/sbt-test/tests/test-quick/src/main/scala/MathFunction.scala

@@ -0,0 +1,3 @@
+object MathFunction {
+  def times2(i: Int): Int = i * 2
+}

sbt-app/src/sbt-test/tests/test-quick/src/test/scala/MathFunctionSpec.scala

@@ -0,0 +1,7 @@
+import org.scalatest.FlatSpec
+
+class MathFunctionTest extends FlatSpec {
+  "times2" should "double the input" in {
+    assert(MathFunction.times2(4) == 8)
+  }
+}

sbt-app/src/sbt-test/tests/test-quick/test

@@ -32,3 +32,9 @@ $ sleep 2000
 -> testQuick Create
 > testQuick Delete
 > testQuick Create
+
+# https://github.com/sbt/sbt/issues/5504
+$ copy-file changed/MathFunction.scala src/test/scala/MathFunction.scala
+> compile
+$ sleep 2000
+-> testQuick MathFunctionTest