diff --git a/bidi.lua b/bidi.lua
index 032b019..1c069ce 100644
--- a/bidi.lua
+++ b/bidi.lua
@@ -207,7 +207,7 @@ assert(
    "EN" == test_output[3].bidi_class
 )
 
-bidi.W3 = function(run)
+local W3 = function(run)
    -- Change al ALs to R.
    for i = 1, #run do
       if "AL" == run[i].bidi_class then
@@ -217,6 +217,19 @@ bidi.W3 = function(run)
    return run
 end
 
+-- Test W3: AL AL AL → R R R
+local test_input = {
+   { ["bidi_class"] = "AL" },
+   { ["bidi_class"] = "AL" },
+   { ["bidi_class"] = "AL" },
+}
+local test_output = W3(test_input)
+assert(
+   "R" == test_output[1].bidi_class and
+   "R" == test_output[2].bidi_class and
+   "R" == test_output[3].bidi_class
+)
+
 bidi.W4 = function(run)
    for i = 1, #run do
       if "ES" == run[i].bidi_class then
@@ -323,7 +336,7 @@ end
 bidi.resolve_weak_types = function(run, sos)
    run = bidi.W1(run, sos)
    run = W2(run, sos)
-   run = bidi.W3(run)
+   run = W3(run)
    run = bidi.W4(run)
    run = bidi.W5(run)
    run = bidi.W6(run)