1 files changed, 47 insertions, 0 deletions
diff --git a/test/test/TestREPL.scala b/test/test/TestREPL.scala
new file mode 100644
index 000000000..d01038c43
--- /dev/null
+++ b/test/test/TestREPL.scala
@@ -0,0 +1,47 @@
+package test
+
+import dotty.tools.dotc.repl._
+import dotty.tools.dotc.core.Contexts.Context
+import collection.mutable
+import java.io.StringWriter
+
+/** A subclass of REPL used for testing.
+ *  It takes a transcript of a REPL session in `script`. The transcript
+ *  starts with the first input prompt `scala> ` and ends with `scala> :quit` and a newline.
+ *  Invoking `process()` on the `TestREPL` runs all input lines and
+ *  collects then interleaved with REPL output in a string writer `out`.
+ *  Invoking `check()` checks that the collected output matches the original
+ *  `script`.
+ */
+class TestREPL(script: String) extends REPL {
+
+  private val out = new StringWriter()
+
+  override lazy val config = new REPL.Config {
+    override val output = new NewLinePrintWriter(out)
+
+    override def input(implicit ctx: Context) = new InteractiveReader {
+      val lines = script.lines
+      def readLine(prompt: String): String = {
+        val line = lines.next
+        if (line.startsWith(prompt) || line.startsWith(continuationPrompt)) {
+          output.println(line)
+          line.drop(prompt.length)
+        }
+        else readLine(prompt)
+      }
+      val interactive = false
+    }
+  }
+
+  def check() = {
+    out.close()
+    val printed = out.toString
+    val transcript = printed.drop(printed.indexOf(config.prompt))
+    if (transcript.toString != script) {
+      println("input differs from transcript:")
+      println(transcript)
+      assert(false)
+    }
+  }
+}
+\ No newline at end of file