Add Utils.makeIdempotent.

The intention is to use this to clean up some of the initialisation
sequences in the front end.

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/unit_tests/utils_test.coffee b/tests/unit_tests/utils_test.coffee
index 67c3b333..9b71ca72 100644
--- a/tests/unit_tests/utils_test.coffee
+++ b/tests/unit_tests/utils_test.coffee
@@ -102,3 +102,26 @@ context "compare versions",
     assert.equal -1, Utils.compareVersions("1.40.1", "1.40.2")
     assert.equal -1, Utils.compareVersions("1.40.1", "1.41")
     assert.equal 1, Utils.compareVersions("1.41", "1.40")
+
+context "makeIdempotent",
+  setup ->
+    @count = 0
+    @func = Utils.makeIdempotent (n = 1) => @count += n
+
+  should "call a function once", ->
+    @func()
+    assert.equal 1, @count
+
+  should "call a function once with an argument", ->
+    @func 2
+    assert.equal 2, @count
+
+  should "not call a function a second time", ->
+    @func()
+    assert.equal 1, @count
+
+  should "not call a function a second time", ->
+    @func()
+    assert.equal 1, @count
+    @func()
+    assert.equal 1, @count