diff --git a/t/pmc/boolean_hll.t b/t/pmc/boolean_hll.t
index 721b7cb..0afb1f1 100644
--- a/t/pmc/boolean_hll.t
+++ b/t/pmc/boolean_hll.t
@@ -34,16 +34,14 @@ Tests C<LuaBoolean> PMC
     set $P0, 1
     $S0 = $P0
     is($S0, 'true', "check HLL")
-    $I0 = isa $P0, 'LuaBoolean'
-    ok($I0)
+    isa_ok($P0, 'LuaBoolean')
 .end
 
 .sub 'check_HLL_const'
     .const 'LuaBoolean' K = '1'
     $S0 = K
     is($S0, 'true', "check HLL & .const")
-    $I0 = isa K, 'LuaBoolean'
-    ok($I0)
+    isa_ok(K, 'LuaBoolean')
 .end
 
 .sub 'check_tostring'
@@ -52,8 +50,7 @@ Tests C<LuaBoolean> PMC
     $S0 = $P0
     is($S0, 'true', "check tostring")
     $P1 = $P0.'tostring'()
-    $I0 = isa $P1, 'LuaString'
-    ok($I0)
+    isa_ok($P1, 'LuaString')
     $S0 = $P1
     is($S0, 'true')
 .end
@@ -64,8 +61,7 @@ Tests C<LuaBoolean> PMC
     $S0 = $P0
     is($S0, 'true', "check tonumber")
     $P1 = $P0.'tonumber'()
-    $I0 = isa $P1, 'LuaNil'
-    ok($I0)
+    isa_ok($P1, 'LuaNil')
 .end
 
 # Local Variables:
diff --git a/t/pmc/function.t b/t/pmc/function.t
index ffd3fde..4399360 100644
--- a/t/pmc/function.t
+++ b/t/pmc/function.t
@@ -83,8 +83,7 @@ Tests C<LuaFunction> PMC
 .sub 'check_logical_not'
     $P0 = new 'LuaFunction'
     $P1 = not $P0
-    $I0 = isa $P1, 'LuaBoolean'
-    ok($I0, "check logical_not")
+    isa_ok($P1, 'LuaBoolean', "check logical_not")
     $S0 = $P1
     is($S0, 'false')
 .end
diff --git a/t/pmc/function_hll.t b/t/pmc/function_hll.t
index 6f09e15..81178fc 100644
--- a/t/pmc/function_hll.t
+++ b/t/pmc/function_hll.t
@@ -35,13 +35,11 @@ Tests C<LuaFunction> PMC
 .sub 'check_HLL'
 #    .const 'LuaFunction' F1 = 'f1'
     .const 'Sub' F1 = 'f1'
-    $I0 = isa F1, 'LuaFunction'
-    ok($I0, "check HLL")
+    isa_ok(F1, 'LuaFunction', "check HLL")
     $S0 = F1()
     is($S0, "f1()")
     .const 'Sub' F2 = 'f2'
-    $I0 = isa F2, 'LuaFunction'
-    ok($I0)
+    isa_ok(F2, 'LuaFunction')
     $S0 = F2()
     is($S0, "f2()")
 .end
@@ -56,11 +54,9 @@ Tests C<LuaFunction> PMC
 
 .sub 'check_HLL_autoboxing'
     $P0 = fct1()
-    $I0 = isa $P0, 'LuaFunction'
-    ok($I0, "check HLL autoboxing")
+    isa_ok($P0, 'LuaFunction', "check HLL autoboxing")
     $P0 = fct2()
-    $I0 = isa $P0, 'LuaFunction'
-    ok($I0)
+    isa_ok($P0, 'LuaFunction')
 .end
 
 .sub 'fct1'
@@ -78,8 +74,7 @@ Tests C<LuaFunction> PMC
     $S0 = $P0
     like($S0, '^function: <[0..9A..Fa..f]>*', "check tostring")
     $P1 = $P0.'tostring'()
-    $I0 = isa $P1, 'LuaString'
-    ok($I0)
+    isa_ok($P1, 'LuaString')
     $S0 = $P1
     like($S0, '^function: <[0..9A..Fa..f]>*')
 .end
@@ -87,15 +82,13 @@ Tests C<LuaFunction> PMC
 .sub 'check_tonumber'
     $P0 = new 'LuaFunction'
     $P1 = $P0.'tonumber'()
-    $I0 = isa $P1, 'LuaNil'
-    ok($I0, "check tonumber")
+    isa_ok($P1, 'LuaNil', "check tonumber")
 .end
 
 .sub 'check_init_pmc'
     .const 'Sub'F1 = 'f1'
     $P0 = new 'LuaFunction', F1
-    $I0 = isa $P0, 'LuaFunction'
-    ok($I0, "check init_pmc")
+    isa_ok($P0, 'LuaFunction', "check init_pmc")
     $S0 = $P0()
     is($S0, "f1()")
 .end
@@ -108,8 +101,7 @@ Tests C<LuaFunction> PMC
     $P1 = get_hll_global '_G'
     .const 'LuaString' k_print = 'print'
     $P2 = $P1[k_print]
-    $I0 = isa $P2, 'LuaFunction'
-    ok($I0, "load from pbc")
+    isa_ok($P2, 'LuaFunction', "load from pbc")
 #    $P2($P2)
 .end
 
@@ -119,8 +111,7 @@ Tests C<LuaFunction> PMC
     $P1 = get_hll_global '_G'
     .const 'LuaString' k_print = 'print'
     $P2 = $P1[k_print]
-    $I0 = isa $P2, 'LuaFunction'
-    ok($I0, "load from pbc")
+    isa_ok($P2, 'LuaFunction', "load from pbc")
 #    $P2($P2)
 .end
 
diff --git a/t/pmc/nil.t b/t/pmc/nil.t
index c64b6a6..2a6a1e8 100644
--- a/t/pmc/nil.t
+++ b/t/pmc/nil.t
@@ -67,8 +67,7 @@ Tests C<LuaNil> PMC
 .sub 'check_logical_not'
     $P0 = new 'LuaNil'
     $P1 = not $P0
-    $I0 = isa $P1, 'LuaBoolean'
-    ok($I0, "check logical_not")
+    isa_ok($P1, 'LuaBoolean', "check logical_not")
     $S0 = $P1
     is($S0, 'true')
 .end
diff --git a/t/pmc/nil_hll.t b/t/pmc/nil_hll.t
index 1e6fe68..15cdec8 100644
--- a/t/pmc/nil_hll.t
+++ b/t/pmc/nil_hll.t
@@ -33,16 +33,14 @@ Tests C<LuaNil> PMC
     $P0 = new 'LuaNil'
     $S0 = $P0
     is($S0, 'nil', "check HLL")
-    $I0 = isa $P0, 'LuaNil'
-    ok($I0)
+    isa_ok($P0, 'LuaNil')
 .end
 
 .sub 'check_HLL_const'
     .const 'LuaNil' K = 'dummy'
     $S0 = K
     is($S0, 'nil', "check HLL & .const")
-    $I0 = isa K, 'LuaNil'
-    ok($I0)
+    isa_ok(K, 'LuaNil')
 .end
 
 .sub 'check_tostring'
@@ -50,8 +48,7 @@ Tests C<LuaNil> PMC
     $S0 = $P0
     is($S0, 'nil', "check tostring")
     $P1 = $P0.'tostring'()
-    $I0 = isa $P1, 'LuaString'
-    ok($I0)
+    isa_ok($P1, 'LuaString')
     $S0 = $P1
     is($S0, 'nil')
 .end
@@ -61,8 +58,7 @@ Tests C<LuaNil> PMC
     $S0 = $P0
     is($S0, 'nil', "check tonumber")
     $P1 = $P0.'tonumber'()
-    $I0 = isa $P1, 'LuaNil'
-    ok($I0)
+    isa_ok($P1, 'LuaNil')
 .end
 
 # Local Variables:
diff --git a/t/pmc/number.t b/t/pmc/number.t
index aef3992..2096f77 100644
--- a/t/pmc/number.t
+++ b/t/pmc/number.t
@@ -56,13 +56,11 @@ Tests C<LuaNumber> PMC
 .sub 'check_set_integer_native'
     $P0 = new 'LuaNumber'
     set $P0, 3.14
-    $I0 = isa $P0, 'LuaNumber'
-    ok($I0, "check set_integer_native")
+    isa_ok($P0, 'LuaNumber', "check set_integer_native")
     $N0 = $P0
     is($N0, 3.14)
     set $P0, 2
-    $I0 = isa $P0, 'LuaNumber'
-    ok($I0)
+    isa_ok($P0, 'LuaNumber')
     $N0 = $P0
     is($N0, 2)
 .end
@@ -71,8 +69,7 @@ Tests C<LuaNumber> PMC
     $P0 = new 'LuaNumber'
     set $P0, 3.14
     $P1 = not $P0
-    $I0 = isa $P1, 'LuaBoolean'
-    ok($I0, "check logical_not")
+    isa_ok($P1, 'LuaBoolean', "check logical_not")
     $S0 = $P1
     is($S0, 'false')
 .end
diff --git a/t/pmc/number_hll.t b/t/pmc/number_hll.t
index 470f6d6..dfd410e 100644
--- a/t/pmc/number_hll.t
+++ b/t/pmc/number_hll.t
@@ -37,16 +37,14 @@ Tests C<LuaNumber> PMC
     set $P0, 3.14
     $N0 = $P0
     is($N0, 3.14, "check HLL")
-    $I0 = isa $P0, 'LuaNumber'
-    ok($I0)
+    isa_ok($P0, 'LuaNumber')
 .end
 
 .sub 'check_HLL_autoboxing'
     $P0 = fct()
     $N0 = $P0
     is($N0, 3.14, "check HLL autoboxing")
-    $I0 = isa $P0, 'LuaNumber'
-    ok($I0)
+    isa_ok($P0, 'LuaNumber')
 .end
 
 .sub 'fct' :anon
@@ -57,24 +55,21 @@ Tests C<LuaNumber> PMC
     .const 'LuaNumber' K = '3.14'
     $N0 = K
     is($N0, 3.14, "check HLL & .const")
-    $I0 = isa K, 'LuaNumber'
-    ok($I0)
+    isa_ok(K, 'LuaNumber')
 .end
 
 .sub 'check_box_float'
     $P0 = box 3.14
     $N0 = $P0
     is($N0, 3.14, "check box float")
-    $I0 = isa $P0, 'LuaNumber'
-    ok($I0)
+    isa_ok($P0, 'LuaNumber')
 .end
 
 .sub 'check_box_integer'
     $P0 = box -2
     $N0 = $P0
     is($N0, -2, "check box integer")
-    $I0 = isa $P0, 'LuaNumber'
-    ok($I0)
+    isa_ok($P0, 'LuaNumber')
 .end
 
 .sub 'check_tostring'
@@ -83,8 +78,7 @@ Tests C<LuaNumber> PMC
     $N0 = $P0
     is($N0, 3.14, "check tostring")
     $P1 = $P0.'tostring'()
-    $I0 = isa $P1, 'LuaString'
-    ok($I0)
+    isa_ok($P1, 'LuaString')
     $S0 = $P1
     is($S0, '3.14')
 .end
@@ -95,8 +89,7 @@ Tests C<LuaNumber> PMC
     $N0 = $P0
     is($N0, 3.14, "check tonumber")
     $P1 = $P0.'tonumber'()
-    $I0 = isa $P1, 'LuaNumber'
-    ok($I0)
+    isa_ok($P1, 'LuaNumber')
     $N0 = $P1
     is($N0, 3.14)
 .end
diff --git a/t/pmc/string.t b/t/pmc/string.t
index f1a59ad..4883b8c 100644
--- a/t/pmc/string.t
+++ b/t/pmc/string.t
@@ -68,8 +68,7 @@ Tests C<LuaString> PMC
     $P0 = new 'LuaString'
     set $P0, 'str'
     $P1 = not $P0
-    $I0 = isa $P1, 'LuaBoolean'
-    ok($I0, "check logical_not")
+    isa_ok($P1, 'LuaBoolean', "check logical_not")
     $S0 = $P1
     is($S0, 'false')
 .end
diff --git a/t/pmc/string_hll.t b/t/pmc/string_hll.t
index a64b719..eae238e 100644
--- a/t/pmc/string_hll.t
+++ b/t/pmc/string_hll.t
@@ -39,16 +39,14 @@ Tests C<LuaString> PMC
     set $P0, "simple string"
     $S0 = $P0
     is($S0, "simple string", "check HLL")
-    $I0 = isa $P0, 'LuaString'
-    ok($I0)
+    isa_ok($P0, 'LuaString')
 .end
 
 .sub 'check_HLL_autoboxing'
     $P0 = fct()
     $S0 = $P0
     is($S0, "simple string", "check HLL autoboxing")
-    $I0 = isa $P0, 'LuaString'
-    ok($I0)
+    isa_ok($P0, 'LuaString')
 .end
 
 .sub 'fct' :anon
@@ -59,24 +57,21 @@ Tests C<LuaString> PMC
     .const 'LuaString' K = "simple string"
     $S0 = K
     is($S0, "simple string", "check HLL & .const")
-    $I0 = isa K, 'LuaString'
-    ok($I0)
+    isa_ok(K, 'LuaString')
 .end
 
 .sub 'check_empty_string'
     .const 'LuaString' K = ''
     $S0 = K
     is($S0, '', "check empty string")
-    $I0 = isa K, 'LuaString'
-    ok($I0)
+    isa_ok(K, 'LuaString')
 .end
 
 .sub 'check_box'
     $P0 = box "simple string"
     $S0 = $P0
     is($S0, "simple string", "check box")
-    $I0 = isa $P0, 'LuaString'
-    ok($I0)
+    isa_ok($P0, 'LuaString')
 .end
 
 .sub 'check_is_equal'
@@ -94,8 +89,7 @@ Tests C<LuaString> PMC
     $S0 = $P0
     is($S0, 'value', "check tostring")
     $P1 = $P0.'tostring'()
-    $I0 = isa $P1, 'LuaString'
-    ok($I0)
+    isa_ok($P1, 'LuaString')
     $S0 = $P1
     is($S0, 'value')
 .end
@@ -106,8 +100,7 @@ Tests C<LuaString> PMC
     $S0 = $P0
     is($S0, '3.14', "check tonumber")
     $P1 = $P0.'tonumber'()
-    $I0 = isa $P1, 'LuaNumber'
-    ok($I0)
+    isa_ok($P1, 'LuaNumber')
     $N0 = $P1
     is($N0, 3.14)
 .end
@@ -118,8 +111,7 @@ Tests C<LuaString> PMC
     $S0 = $P0
     is($S0, '111', "check tobase")
     $P1 = $P0.'tobase'(2)
-    $I0 = isa $P1, 'LuaNumber'
-    ok($I0)
+    isa_ok($P1, 'LuaNumber')
     $I0 = $P1
     is($I0, 7)
 .end
diff --git a/t/pmc/table.t b/t/pmc/table.t
index 39a2f57..de022a3 100644
--- a/t/pmc/table.t
+++ b/t/pmc/table.t
@@ -72,8 +72,7 @@ Tests C<table> type
 .sub 'check_logical_not'
     $P0 = new 'LuaTable'
     $P1 = not $P0
-    $I0 = isa $P1, 'LuaBoolean'
-    ok($I0, "check logical_not")
+    isa_ok($P1, 'LuaBoolean', "check logical_not")
     $S0 = $P1
     is($S0, 'false')
 .end
diff --git a/t/pmc/table_hll.t b/t/pmc/table_hll.t
index 192f650..32216bf 100644
--- a/t/pmc/table_hll.t
+++ b/t/pmc/table_hll.t
@@ -32,8 +32,7 @@ Tests C<table> type
 
 .sub 'check_HLL'
     $P0 = new 'LuaTable'
-    $I0 = isa $P0, 'LuaTable'
-    ok($I0, "check HLL")
+    isa_ok($P0, 'LuaTable', "check HLL")
 .end
 
 .sub 'check_len'
@@ -120,8 +119,7 @@ Tests C<table> type
     $S0 = $P0
     like($S0, '^table: <[0..9A..Fa..f]>*', "check tostring")
     $P1 = $P0.'tostring'()
-    $I0 = isa $P1, 'LuaString'
-    ok($I0)
+    isa_ok($P1, 'LuaString')
     $S0 = $P1
     like($S0, '^table: <[0..9A..Fa..f]>*')
 .end
@@ -129,8 +127,7 @@ Tests C<table> type
 .sub 'check_tonumber'
     $P0 = new 'LuaTable'
     $P1 = $P0.'tonumber'()
-    $I0 = isa $P1, 'LuaNil'
-    ok($I0, "check tonumber")
+    isa_ok($P1, 'LuaNil', "check tonumber")
 .end
 
 # Local Variables:
diff --git a/t/pmc/thread.t b/t/pmc/thread.t
index b6afca1..91aefe9 100644
--- a/t/pmc/thread.t
+++ b/t/pmc/thread.t
@@ -81,8 +81,7 @@ Tests Lua C<thread> type
     .const 'Sub' F1 = 'f1'
     $P0 = new 'LuaThread', F1
     $P1 = not $P0
-    $I0 = isa $P1, 'LuaBoolean'
-    ok($I0, "check logical_not")
+    isa_ok($P1, 'LuaBoolean', "check logical_not")
     $S0 = $P1
     is($S0, 'false')
 .end
diff --git a/t/pmc/thread_hll.t b/t/pmc/thread_hll.t
index e5e4bd1..d51014f 100644
--- a/t/pmc/thread_hll.t
+++ b/t/pmc/thread_hll.t
@@ -34,8 +34,7 @@ Tests Lua C<thread> type
 .sub 'check_HLL'
     .const 'Sub' F1 = 'f1'
     $P0 = new 'LuaThread', F1
-    $I0 = isa $P0, 'LuaThread'
-    ok($I0, "check HLL")
+    isa_ok($P0, 'LuaThread', "check HLL")
 .end
 
 .sub 'f1'
@@ -49,8 +48,7 @@ Tests Lua C<thread> type
     $S0 = $P0
     like($S0, '^thread: <[0..9A..Fa..f]>*', "check tostring")
     $P1 = $P0.'tostring'()
-    $I0 = isa $P1, 'LuaString'
-    ok($I0)
+    isa_ok($P1, 'LuaString')
     $S0 = $P1
     like($S0, '^thread: <[0..9A..Fa..f]>*')
 .end
@@ -59,8 +57,7 @@ Tests Lua C<thread> type
     .const 'Sub' F1 = 'f1'
     $P0 = new 'LuaThread', F1
     $P1 = $P0.'tonumber'()
-    $I0 = isa $P1, 'LuaNil'
-    ok($I0, "check tonumber")
+    isa_ok($P1, 'LuaNil', "check tonumber")
 .end
 
 .sub 'check__add'
diff --git a/t/pmc/userdata.t b/t/pmc/userdata.t
index d31c744..04e1872 100644
--- a/t/pmc/userdata.t
+++ b/t/pmc/userdata.t
@@ -73,8 +73,7 @@ Tests C<userdata> type
     $P1 = new 'Array'
     setattribute $P0, 'data', $P1
     $P2 = not $P0
-    $I0 = isa $P2, 'LuaBoolean'
-    ok($I0, "check logical_not")
+    isa_ok($P2, 'LuaBoolean', "check logical_not")
     $S0 = $P2
     is($S0, 'false')
 .end
diff --git a/t/pmc/userdata_hll.t b/t/pmc/userdata_hll.t
index 1a52ea6..c4cf492 100644
--- a/t/pmc/userdata_hll.t
+++ b/t/pmc/userdata_hll.t
@@ -32,8 +32,7 @@ Tests C<userdata> type
     $P0 = new 'LuaUserdata'
     $P1 = new 'Array'
     setattribute $P0, 'data', $P1
-    $I0 = isa $P0, 'LuaUserdata'
-    ok($I0, "check HLL")
+    isa_ok($P0, 'LuaUserdata', "check HLL")
 .end
 
 .sub 'check_tostring'
@@ -43,8 +42,7 @@ Tests C<userdata> type
     $S0 = $P0
     like($S0, '^userdata: <[0..9A..Fa..f]>*', "check tostring")
     $P2 = $P0.'tostring'()
-    $I0 = isa $P2, 'LuaString'
-    ok($I0)
+    isa_ok($P2, 'LuaString')
     $S0 = $P2
     like($S0, '^userdata: <[0..9A..Fa..f]>*')
 .end
@@ -54,8 +52,7 @@ Tests C<userdata> type
     $P1 = new 'Array'
     setattribute $P0, 'data', $P1
     $P2 = $P0.'tonumber'()
-    $I0 = isa $P2, 'LuaNil'
-    ok($I0, "check tonumber")
+    isa_ok($P2, 'LuaNil', "check tonumber")
 .end
 
 # Local Variables: