From 404a677955ae54fdfabb8d1001a5ed7a80778044 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Sun, 5 Nov 2017 08:23:21 -0800
Subject: More `ApplicativeTests`

---
 core/src/test/scala/forge/ApplicativeTests.scala | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

(limited to 'core/src/test/scala/forge/ApplicativeTests.scala')

diff --git a/core/src/test/scala/forge/ApplicativeTests.scala b/core/src/test/scala/forge/ApplicativeTests.scala
index 462cb180..000554ef 100644
--- a/core/src/test/scala/forge/ApplicativeTests.scala
+++ b/core/src/test/scala/forge/ApplicativeTests.scala
@@ -71,10 +71,9 @@ object ApplicativeTests extends TestSuite {
       assert(res == Some("lol hello"))
     }
     'upstreamAlwaysEvaluated - {
-      // Validate the assumption that whether or not control-flow reaches the
-      // Applyable#apply call inside an Opt{...} block, we always evaluate the
-      // LHS of the Applyable#apply because it gets lifted out of any control
-      // flow statements
+      // Whether or not control-flow reaches the Applyable#apply call inside an
+      // Opt{...} block, we always evaluate the LHS of the Applyable#apply
+      // because it gets lifted out of any control flow statements
       val counter = new Counter()
       def up = Opt{ "lol " + counter() }
       val down = Opt{ if ("lol".length > 10) up() else "fail" }
@@ -83,6 +82,18 @@ object ApplicativeTests extends TestSuite {
         counter.value == 1
       )
     }
+    'upstreamEvaluatedOnlyOnce - {
+      // Even if control-flow reaches the Applyable#apply call more than once,
+      // it only gets evaluated once due to its lifting out of the Opt{...} block
+      val counter = new Counter()
+      def up = Opt{ "lol " + counter() }
+      def runTwice[T](t: => T) = (t, t)
+      val down = Opt{ runTwice(up()) }
+      assert(
+        down == Some(("lol 1", "lol 1")),
+        counter.value == 1
+      )
+    }
   }
 }
 
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