diff --git a/bidi.lua b/bidi.lua
index d98eb9b..c2a694f 100644
--- a/bidi.lua
+++ b/bidi.lua
@@ -135,76 +135,133 @@ local W2 = function(run, sos)
    return run
 end
 
--- Test W2: AL EN → AL AN
-local test_input = {
-   { ["bidi_class"] = "AL" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W2(test_input, "L")
-assert(
-   "AL" == test_output[1].bidi_class and
-   "AN" == test_output[2].bidi_class
+dump_table = function(table_, indentation)
+   assert( "table" == type(table_) )
+
+   local indentation = indentation or 0
+   assert( "number" == type(indentation) )
+
+   local result = {}
+   for key, value in pairs(table_) do
+      local prefix = "\n" .. ("   "):rep(indentation) .. key .. ": "
+      if "table" == type(value) then
+         result[#result + 1] = prefix .. dump_table(value, indentation + 1)
+      else
+         result[#result + 1] = prefix .. tostring(value)
+      end
+   end
+   return table.concat(result)
+end
+
+local test_rule = function(
+      description,
+      rule,
+      test_input,
+      expected_output,
+      ...
+)
+   assert( "string" == type(description) )
+   assert( "function" == type(rule) )
+   assert( "table" == type(test_input) )
+   assert( "table" == type(expected_output) )
+   local test_output = rule(test_input, ...)
+   for i = 1, #test_input do
+      assert(
+         test_output[i].bidi_class == expected_output[i].bidi_class,
+         description ..
+         dump_table(test_output)
+      )
+   end
+end
+
+test_rule(
+   "Test W2: AL EN → AL AN",
+   W2,
+   {
+      { ["bidi_class"] = "AL" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "AL" },
+      { ["bidi_class"] = "AN" },
+   },
+   "L"
 )
 
--- Test W2: AL NI EN → AL NI AN
-local test_input = {
-   { ["bidi_class"] = "AL" },
-   { ["bidi_class"] = "NI" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W2(test_input, "L")
-assert(
-   "AL" == test_output[1].bidi_class and
-   "NI" == test_output[2].bidi_class and
-   "AN" == test_output[3].bidi_class
+test_rule(
+   "Test W2: AL NI EN → AL NI AN",
+   W2,
+   {
+      { ["bidi_class"] = "AL" },
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "AL" },
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "AN" },
+   },
+   "L"
 )
 
--- Test W2: sos NI EN → sos NI EN (sos = L)
-local test_input = {
-   { ["bidi_class"] = "NI" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W2(test_input, "L")
-assert(
-   "NI" == test_output[1].bidi_class and
-   "EN" == test_output[2].bidi_class
+test_rule(
+   "Test W2: sos NI EN → sos NI EN (sos = L)",
+   W2,
+   {
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   "L"
 )
 
--- Test W2: sos NI EN → sos NI EN (sos = R)
-local test_input = {
-   { ["bidi_class"] = "NI" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W2(test_input, "R")
-assert(
-   "NI" == test_output[1].bidi_class and
-   "EN" == test_output[2].bidi_class
+test_rule(
+   "Test W2: sos NI EN → sos NI EN (sos = R)",
+   W2,
+   {
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   "R"
 )
 
--- Test W2: L NI EN → L NI AN
-local test_input = {
-   { ["bidi_class"] = "L" },
-   { ["bidi_class"] = "NI" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W2(test_input, "L")
-assert(
-   "L" == test_output[1].bidi_class and
-   "NI" == test_output[2].bidi_class and
-   "EN" == test_output[3].bidi_class
+test_rule(
+   "Test W2: L NI EN → L NI EN",
+   W2,
+   {
+      { ["bidi_class"] = "L" },
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "L" },
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   "L"
 )
 
--- Test W2: R NI EN → R NI AN
-local test_input = {
-   { ["bidi_class"] = "R" },
-   { ["bidi_class"] = "NI" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W2(test_input, "L")
-assert(
-   "R" == test_output[1].bidi_class and
-   "NI" == test_output[2].bidi_class and
-   "EN" == test_output[3].bidi_class
+test_rule(
+   "Test W2: R NI EN → R NI EN",
+   W2,
+   {
+      { ["bidi_class"] = "R" },
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "R" },
+      { ["bidi_class"] = "NI" },
+      { ["bidi_class"] = "EN" },
+   },
+   "L"
 )
 
 local W3 = function(run)
@@ -217,17 +274,19 @@ local 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
+test_rule(
+   "Test W3: AL AL AL → R R R",
+   W3,
+   {
+      { ["bidi_class"] = "AL" },
+      { ["bidi_class"] = "AL" },
+      { ["bidi_class"] = "AL" },
+   },
+   {
+      { ["bidi_class"] = "R" },
+      { ["bidi_class"] = "R" },
+      { ["bidi_class"] = "R" },
+   }
 )
 
 local W4 = function(run)
@@ -268,43 +327,49 @@ local W4 = function(run)
    return run
 end
 
--- Test W4: EN ES EN → EN EN EN
-local test_input = {
-   { ["bidi_class"] = "EN" },
-   { ["bidi_class"] = "ES" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W4(test_input)
-assert(
-   "EN" == test_output[1].bidi_class and
-   "EN" == test_output[2].bidi_class and
-   "EN" == test_output[3].bidi_class
+test_rule(
+   "Test·W4:·EN·ES·EN·→·EN·EN·EN",
+   W4,
+   {
+      { ["bidi_class"] = "EN" },
+      { ["bidi_class"] = "ES" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "EN" },
+      { ["bidi_class"] = "EN" },
+      { ["bidi_class"] = "EN" },
+   }
 )
 
--- Test W4: EN CS EN → EN EN EN
-local test_input = {
-   { ["bidi_class"] = "EN" },
-   { ["bidi_class"] = "CS" },
-   { ["bidi_class"] = "EN" },
-}
-local test_output = W4(test_input)
-assert(
-   "EN" == test_output[1].bidi_class and
-   "EN" == test_output[2].bidi_class and
-   "EN" == test_output[3].bidi_class
+test_rule(
+   "Test·W4:·EN·CS·EN·→·EN·EN·EN",
+   W4,
+   {
+      { ["bidi_class"] = "EN" },
+      { ["bidi_class"] = "CS" },
+      { ["bidi_class"] = "EN" },
+   },
+   {
+      { ["bidi_class"] = "EN" },
+      { ["bidi_class"] = "EN" },
+      { ["bidi_class"] = "EN" },
+   }
 )
 
--- Test W4: AN CS AN → AN AN AN
-local test_input = {
-   { ["bidi_class"] = "AN" },
-   { ["bidi_class"] = "CS" },
-   { ["bidi_class"] = "AN" },
-}
-local test_output = W4(test_input)
-assert(
-   "AN" == test_output[1].bidi_class and
-   "AN" == test_output[2].bidi_class and
-   "AN" == test_output[3].bidi_class
+test_rule(
+   "Test·W4:·AN·CS·AN·→·AN·AN·AN",
+   W4,
+   {
+      { ["bidi_class"] = "AN" },
+      { ["bidi_class"] = "CS" },
+      { ["bidi_class"] = "AN" },
+   },
+   {
+      { ["bidi_class"] = "AN" },
+      { ["bidi_class"] = "AN" },
+      { ["bidi_class"] = "AN" },
+   }
 )
 
 bidi.W5 = function(run)