diff --git a/.gitignore b/.gitignore
index cc0e3da8..6c1ef4ff 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 deps
 *.o
 *.beam
+*.erltypes
 *.plt
 /.dialyzer_plt
 *~
diff --git a/Makefile b/Makefile
index 0eddb11c..34a8b53d 100644
--- a/Makefile
+++ b/Makefile
@@ -107,7 +107,7 @@ clean:
 	rm -rf bin/gradualizer ebin cover test/*.beam
 
 .PHONY: tests eunit compile-tests cli-tests
-tests: build_test_data eunit cli-tests
+tests: check_name_clashes build_test_data eunit cli-tests
 
 test_erls=$(wildcard test/*.erl)
 test_beams=$(test_erls:test/%.erl=test/%.beam)
@@ -212,6 +212,14 @@ DIALYZER_OPTS ?= -Werror_handling -Wrace_conditions
 dialyze: app $(DIALYZER_PLT)
 	dialyzer $(DIALYZER_OPTS) ebin
 
+.PHONY: dialyze-tests
+dialyze-tests: app $(DIALYZER_PLT)
+	dialyzer $(DIALYZER_OPTS) $(test_data_erls)
+
+.PHONY: check_name_clashes
+check_name_clashes:
+	test/check_name_clashes.sh
+
 # DIALYZER_PLT is a variable understood directly by Dialyzer.
 # Exit status 2 = warnings were emitted
 $(DIALYZER_PLT):
diff --git a/test/check_name_clashes.sh b/test/check_name_clashes.sh
new file mode 100755
index 00000000..681a1cfa
--- /dev/null
+++ b/test/check_name_clashes.sh
@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+#set -x
+
+if [ x$(uname) == x"Darwin" ]; then
+BASENAME=basename
+else
+BASENAME="basename -a"
+fi
+
+UNIQ=$(find test/should_pass test/should_fail test/known_problems/*/ -name \*.erl \
+        | xargs $BASENAME \
+        | sort \
+        | uniq -c \
+        | sort -n \
+        | tail -1)
+
+COUNT=$(echo $UNIQ | awk '{print $1}')
+
+if [ "$COUNT" == 1 ]; then
+    exit 0
+else
+    echo "Name clash in tests:"
+    find test -name $(echo $UNIQ | awk '{print $2}')
+    exit 1
+fi
diff --git a/test/known_problems/should_fail/guard_fail.erl b/test/known_problems/should_fail/guard_should_fail.erl
similarity index 88%
rename from test/known_problems/should_fail/guard_fail.erl
rename to test/known_problems/should_fail/guard_should_fail.erl
index 2d6bbc28..eb38c430 100644
--- a/test/known_problems/should_fail/guard_fail.erl
+++ b/test/known_problems/should_fail/guard_should_fail.erl
@@ -1,4 +1,4 @@
--module(guard_fail).
+-module(guard_should_fail).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/known_problems/should_fail/intersection_with_any_fail.erl b/test/known_problems/should_fail/intersection_with_any_should_fail.erl
similarity index 94%
rename from test/known_problems/should_fail/intersection_with_any_fail.erl
rename to test/known_problems/should_fail/intersection_with_any_should_fail.erl
index 9c3cd4f5..ceab9fb6 100644
--- a/test/known_problems/should_fail/intersection_with_any_fail.erl
+++ b/test/known_problems/should_fail/intersection_with_any_should_fail.erl
@@ -1,4 +1,4 @@
--module(intersection_with_any_fail).
+-module(intersection_with_any_should_fail).
 
 -export([any_refined_using_guard/1,
          var_as_pattern/1,
diff --git a/test/known_problems/should_fail/rigid_type_variables.erl b/test/known_problems/should_fail/rigid_type_variables_fail.erl
similarity index 69%
rename from test/known_problems/should_fail/rigid_type_variables.erl
rename to test/known_problems/should_fail/rigid_type_variables_fail.erl
index 1e61b227..3108ba02 100644
--- a/test/known_problems/should_fail/rigid_type_variables.erl
+++ b/test/known_problems/should_fail/rigid_type_variables_fail.erl
@@ -1,4 +1,4 @@
--module(rigid_type_variables).
+-module(rigid_type_variables_fail).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/known_problems/should_pass/rigid_type_variables.erl b/test/known_problems/should_pass/rigid_type_variables_pass.erl
similarity index 81%
rename from test/known_problems/should_pass/rigid_type_variables.erl
rename to test/known_problems/should_pass/rigid_type_variables_pass.erl
index 924ef318..ea5bc05e 100644
--- a/test/known_problems/should_pass/rigid_type_variables.erl
+++ b/test/known_problems/should_pass/rigid_type_variables_pass.erl
@@ -1,4 +1,4 @@
--module(rigid_type_variables).
+-module(rigid_type_variables_pass).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_fail/arith_op.erl b/test/should_fail/arith_op_fail.erl
similarity index 98%
rename from test/should_fail/arith_op.erl
rename to test/should_fail/arith_op_fail.erl
index 9019a491..93f286de 100644
--- a/test/should_fail/arith_op.erl
+++ b/test/should_fail/arith_op_fail.erl
@@ -1,4 +1,5 @@
--module(arith_op).
+-module(arith_op_fail).
+
 -export([failplus/1, faildivvar/1, faildivlit/1, failpositivedivision/1,
          faildivprecise/1, failplusprecise/2, failminusprecisepos/2,
          failminusnonneg/2, failminuspreciseneg/2,
diff --git a/test/should_fail/bc.erl b/test/should_fail/bc_fail.erl
similarity index 94%
rename from test/should_fail/bc.erl
rename to test/should_fail/bc_fail.erl
index b46ce780..62f73094 100644
--- a/test/should_fail/bc.erl
+++ b/test/should_fail/bc_fail.erl
@@ -1,4 +1,4 @@
--module(bc).
+-module(bc_fail).
 -export([f/0, non_bin_expr/0, integer_signed_wrong/1]).
 
 -spec f() -> binary().
diff --git a/test/should_fail/catch_expr.erl b/test/should_fail/catch_expr_fail.erl
similarity index 75%
rename from test/should_fail/catch_expr.erl
rename to test/should_fail/catch_expr_fail.erl
index d7f32060..7db7d304 100644
--- a/test/should_fail/catch_expr.erl
+++ b/test/should_fail/catch_expr_fail.erl
@@ -1,4 +1,4 @@
--module(catch_expr).
+-module(catch_expr_fail).
 
 -export([foo/1]).
 
diff --git a/test/should_fail/covariant_map_keys.erl b/test/should_fail/covariant_map_keys_fail.erl
similarity index 89%
rename from test/should_fail/covariant_map_keys.erl
rename to test/should_fail/covariant_map_keys_fail.erl
index 9db1770c..99c5883b 100644
--- a/test/should_fail/covariant_map_keys.erl
+++ b/test/should_fail/covariant_map_keys_fail.erl
@@ -1,4 +1,4 @@
--module(covariant_map_keys).
+-module(covariant_map_keys_fail).
 
 -compile([nowarn_unused_function]).
 -export([not_good/1]).
diff --git a/test/should_fail/intersection_with_any.erl b/test/should_fail/intersection_with_any_fail.erl
similarity index 82%
rename from test/should_fail/intersection_with_any.erl
rename to test/should_fail/intersection_with_any_fail.erl
index f14777c6..915dc972 100644
--- a/test/should_fail/intersection_with_any.erl
+++ b/test/should_fail/intersection_with_any_fail.erl
@@ -1,4 +1,4 @@
--module(intersection_with_any).
+-module(intersection_with_any_fail).
 
 -export([intersection_using_constraints/1]).
 
diff --git a/test/should_fail/list_infer.erl b/test/should_fail/list_infer_fail.erl
similarity index 81%
rename from test/should_fail/list_infer.erl
rename to test/should_fail/list_infer_fail.erl
index dc155b6c..59876421 100644
--- a/test/should_fail/list_infer.erl
+++ b/test/should_fail/list_infer_fail.erl
@@ -1,4 +1,4 @@
--module(list_infer).
+-module(list_infer_fail).
 
 -gradualizer(infer).
 -export([f/0]).
diff --git a/test/should_fail/messaging.erl b/test/should_fail/messaging_fail.erl
similarity index 96%
rename from test/should_fail/messaging.erl
rename to test/should_fail/messaging_fail.erl
index 9b8d276f..5016c4a5 100644
--- a/test/should_fail/messaging.erl
+++ b/test/should_fail/messaging_fail.erl
@@ -1,4 +1,4 @@
--module(messaging).
+-module(messaging_fail).
 
 -export([server1/0, server2/0, server3/0, server4/0]).
 
diff --git a/test/should_fail/named_fun.erl b/test/should_fail/named_fun_fail.erl
similarity index 88%
rename from test/should_fail/named_fun.erl
rename to test/should_fail/named_fun_fail.erl
index 5fab8527..17d3938b 100644
--- a/test/should_fail/named_fun.erl
+++ b/test/should_fail/named_fun_fail.erl
@@ -1,4 +1,4 @@
--module(named_fun).
+-module(named_fun_fail).
 
 -export([bar/0, baz/1]).
 
diff --git a/test/should_fail/named_fun_infer.erl b/test/should_fail/named_fun_infer_fail.erl
similarity index 92%
rename from test/should_fail/named_fun_infer.erl
rename to test/should_fail/named_fun_infer_fail.erl
index f4a82621..72978a15 100644
--- a/test/should_fail/named_fun_infer.erl
+++ b/test/should_fail/named_fun_infer_fail.erl
@@ -1,4 +1,4 @@
--module(named_fun_infer).
+-module(named_fun_infer_fail).
 
 -gradualizer(infer).
 -export([bar/0, sum/1]).
diff --git a/test/should_fail/operator_pattern.erl b/test/should_fail/operator_pattern_fail.erl
similarity index 78%
rename from test/should_fail/operator_pattern.erl
rename to test/should_fail/operator_pattern_fail.erl
index bfaded21..08f0464b 100644
--- a/test/should_fail/operator_pattern.erl
+++ b/test/should_fail/operator_pattern_fail.erl
@@ -1,4 +1,4 @@
--module(operator_pattern).
+-module(operator_pattern_fail).
 -export([n/1, p/1]).
 
 -spec n(non_neg_integer()) -> {}.
diff --git a/test/should_fail/record_refinement_fail.erl b/test/should_fail/record_refinement_fail.erl
index 0d2b26ff..448e04ad 100644
--- a/test/should_fail/record_refinement_fail.erl
+++ b/test/should_fail/record_refinement_fail.erl
@@ -16,6 +16,8 @@ one_field2(_, I) -> I.
 -spec refined_field(#refined_field{}) -> #refined_field{f :: integer()}.
 refined_field(R) -> R.
 
+%% The refinement in the result type is not handled by Dialyzer - it will error out.
+%% Comment it out if trying to run `make dialyze-tests'.
 -spec refined_field2(#refined_field{}) -> #refined_field{f :: atom()}.
 refined_field2(#refined_field{f = undefined}) -> #refined_field{f = 0};
 refined_field2(R) -> R.
diff --git a/test/should_fail/record_wildcard.erl b/test/should_fail/record_wildcard_fail.erl
similarity index 91%
rename from test/should_fail/record_wildcard.erl
rename to test/should_fail/record_wildcard_fail.erl
index 2553f551..be0e66de 100644
--- a/test/should_fail/record_wildcard.erl
+++ b/test/should_fail/record_wildcard_fail.erl
@@ -1,4 +1,4 @@
--module(record_wildcard).
+-module(record_wildcard_fail).
 
 -export([f/0, g/0]).
 
diff --git a/test/should_fail/send.erl b/test/should_fail/send_fail.erl
similarity index 87%
rename from test/should_fail/send.erl
rename to test/should_fail/send_fail.erl
index 75cd7a4c..aa5420a6 100644
--- a/test/should_fail/send.erl
+++ b/test/should_fail/send_fail.erl
@@ -1,4 +1,4 @@
--module(send).
+-module(send_fail).
 
 -export([foo/2, bar/2]).
 
diff --git a/test/should_fail/shortcut_ops.erl b/test/should_fail/shortcut_ops_fail.erl
similarity index 94%
rename from test/should_fail/shortcut_ops.erl
rename to test/should_fail/shortcut_ops_fail.erl
index 8e1b317b..d5b8d4f8 100644
--- a/test/should_fail/shortcut_ops.erl
+++ b/test/should_fail/shortcut_ops_fail.erl
@@ -1,4 +1,4 @@
--module(shortcut_ops).
+-module(shortcut_ops_fail).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_fail/tuple_union.erl b/test/should_fail/tuple_union.erl
deleted file mode 100644
index b3aadfb6..00000000
--- a/test/should_fail/tuple_union.erl
+++ /dev/null
@@ -1,7 +0,0 @@
--module(tuple_union).
-
--export([tuple_union/0]).
-
--spec tuple_union() -> {undefined, binary()} | {integer(), undefined}.
-tuple_union() ->
-    {undefined, undefined}.
diff --git a/test/should_fail/tuple_union_fail.erl b/test/should_fail/tuple_union_fail.erl
index 91601e17..a510e3ff 100644
--- a/test/should_fail/tuple_union_fail.erl
+++ b/test/should_fail/tuple_union_fail.erl
@@ -1,7 +1,12 @@
 -module(tuple_union_fail).
 
 -export([f/0]).
+-export([tuple_union/0]).
 
 -spec f() -> {integer()} | {boolean()}.
 f() ->
     {apa}.
+
+-spec tuple_union() -> {undefined, binary()} | {integer(), undefined}.
+tuple_union() ->
+    {undefined, undefined}.
diff --git a/test/should_fail/type_refinement.erl b/test/should_fail/type_refinement_fail.erl
similarity index 97%
rename from test/should_fail/type_refinement.erl
rename to test/should_fail/type_refinement_fail.erl
index d6cf0f57..cb83c751 100644
--- a/test/should_fail/type_refinement.erl
+++ b/test/should_fail/type_refinement_fail.erl
@@ -1,4 +1,4 @@
--module(type_refinement).
+-module(type_refinement_fail).
 -export([guard_prevents_refinement/2, imprecision_prevents_refinement/2,
          multi_pat_fail_1/2,
          guard_prevents_refinement2/1,
diff --git a/test/should_pass/bc.erl b/test/should_pass/bc_pass.erl
similarity index 99%
rename from test/should_pass/bc.erl
rename to test/should_pass/bc_pass.erl
index dda34365..dc5389ab 100644
--- a/test/should_pass/bc.erl
+++ b/test/should_pass/bc_pass.erl
@@ -1,4 +1,4 @@
--module(bc).
+-module(bc_pass).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_pass/catch_expr.erl b/test/should_pass/catch_expr_pass.erl
similarity index 74%
rename from test/should_pass/catch_expr.erl
rename to test/should_pass/catch_expr_pass.erl
index 97b64324..b07c0536 100644
--- a/test/should_pass/catch_expr.erl
+++ b/test/should_pass/catch_expr_pass.erl
@@ -1,4 +1,4 @@
--module(catch_expr).
+-module(catch_expr_pass).
 
 -export([foo/1]).
 
diff --git a/test/should_pass/covariant_map_keys.erl b/test/should_pass/covariant_map_keys_pass.erl
similarity index 81%
rename from test/should_pass/covariant_map_keys.erl
rename to test/should_pass/covariant_map_keys_pass.erl
index c2ccf4b4..352c63d1 100644
--- a/test/should_pass/covariant_map_keys.erl
+++ b/test/should_pass/covariant_map_keys_pass.erl
@@ -1,4 +1,4 @@
--module(covariant_map_keys).
+-module(covariant_map_keys_pass).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_pass/intersection.erl b/test/should_pass/intersection_pass.erl
similarity index 87%
rename from test/should_pass/intersection.erl
rename to test/should_pass/intersection_pass.erl
index d00a2d03..be36aae7 100644
--- a/test/should_pass/intersection.erl
+++ b/test/should_pass/intersection_pass.erl
@@ -1,4 +1,4 @@
--module(intersection).
+-module(intersection_pass).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_pass/intersection_with_any.erl b/test/should_pass/intersection_with_any_pass.erl
similarity index 94%
rename from test/should_pass/intersection_with_any.erl
rename to test/should_pass/intersection_with_any_pass.erl
index b1d1b654..4084ddc6 100644
--- a/test/should_pass/intersection_with_any.erl
+++ b/test/should_pass/intersection_with_any_pass.erl
@@ -1,4 +1,4 @@
--module(intersection_with_any).
+-module(intersection_with_any_pass).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_pass/list_infer.erl b/test/should_pass/list_infer_pass.erl
similarity index 85%
rename from test/should_pass/list_infer.erl
rename to test/should_pass/list_infer_pass.erl
index afb89ba4..04095da2 100644
--- a/test/should_pass/list_infer.erl
+++ b/test/should_pass/list_infer_pass.erl
@@ -1,4 +1,4 @@
--module(list_infer).
+-module(list_infer_pass).
 
 -gradualizer(infer).
 -export([f/0]).
diff --git a/test/should_pass/messaging.erl b/test/should_pass/messaging_pass.erl
similarity index 97%
rename from test/should_pass/messaging.erl
rename to test/should_pass/messaging_pass.erl
index 1a315662..44fa4990 100644
--- a/test/should_pass/messaging.erl
+++ b/test/should_pass/messaging_pass.erl
@@ -1,4 +1,4 @@
--module(messaging).
+-module(messaging_pass).
 
 -export([main/0, server/0, server1/0, server2/0, server3/0, server4/0]).
 
diff --git a/test/should_pass/named_fun_infer.erl b/test/should_pass/named_fun_infer_pass.erl
similarity index 92%
rename from test/should_pass/named_fun_infer.erl
rename to test/should_pass/named_fun_infer_pass.erl
index 87b4798d..ac4dd10c 100644
--- a/test/should_pass/named_fun_infer.erl
+++ b/test/should_pass/named_fun_infer_pass.erl
@@ -1,4 +1,4 @@
--module(named_fun_infer).
+-module(named_fun_infer_pass).
 
 -gradualizer(infer).
 -export([atom_sum/1]).
diff --git a/test/should_pass/named_fun.erl b/test/should_pass/named_fun_pass.erl
similarity index 95%
rename from test/should_pass/named_fun.erl
rename to test/should_pass/named_fun_pass.erl
index f11a632d..7ad911d6 100644
--- a/test/should_pass/named_fun.erl
+++ b/test/should_pass/named_fun_pass.erl
@@ -1,4 +1,4 @@
--module(named_fun).
+-module(named_fun_pass).
 
 -export([fac/1, sum/1]).
 
diff --git a/test/should_pass/operator_pattern.erl b/test/should_pass/operator_pattern_pass.erl
similarity index 97%
rename from test/should_pass/operator_pattern.erl
rename to test/should_pass/operator_pattern_pass.erl
index 60bf25c8..f4bc3dd3 100644
--- a/test/should_pass/operator_pattern.erl
+++ b/test/should_pass/operator_pattern_pass.erl
@@ -1,4 +1,4 @@
--module(operator_pattern).
+-module(operator_pattern_pass).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_pass/record_wildcard.erl b/test/should_pass/record_wildcard_pass.erl
similarity index 93%
rename from test/should_pass/record_wildcard.erl
rename to test/should_pass/record_wildcard_pass.erl
index 0177be00..c54aea5e 100644
--- a/test/should_pass/record_wildcard.erl
+++ b/test/should_pass/record_wildcard_pass.erl
@@ -1,4 +1,4 @@
--module(record_wildcard).
+-module(record_wildcard_pass).
 
 -export([f/0, g/0, h/1]).
 
diff --git a/test/should_pass/records.erl b/test/should_pass/records.erl
index da736595..3916d926 100644
--- a/test/should_pass/records.erl
+++ b/test/should_pass/records.erl
@@ -1,9 +1,10 @@
 -module(records).
 
--export([f/0, g/1, h/0, i/0, j/0, k/0, l/0,
+-export([f/0, f/1, g/1, h/0, i/0, j/0, k/0, l/0,
          rec_field_subtype/1,
          rec_index_subtype/0,
-         record_as_tuple/1]).
+         record_as_tuple/1,
+         nospec_update_bug/1]).
 
 -record(r, {f1     :: atom(),
             f2 = 1 :: integer()}).
diff --git a/test/should_pass/send.erl b/test/should_pass/send_pass.erl
similarity index 87%
rename from test/should_pass/send.erl
rename to test/should_pass/send_pass.erl
index d0671634..2bf450cb 100644
--- a/test/should_pass/send.erl
+++ b/test/should_pass/send_pass.erl
@@ -1,4 +1,4 @@
--module(send).
+-module(send_pass).
 
 -export([foo/2, bar/2]).
 
diff --git a/test/should_pass/shortcut_ops.erl b/test/should_pass/shortcut_ops_pass.erl
similarity index 98%
rename from test/should_pass/shortcut_ops.erl
rename to test/should_pass/shortcut_ops_pass.erl
index 426bcb89..1d5dcd02 100644
--- a/test/should_pass/shortcut_ops.erl
+++ b/test/should_pass/shortcut_ops_pass.erl
@@ -1,4 +1,4 @@
--module(shortcut_ops).
+-module(shortcut_ops_pass).
 
 -compile([export_all, nowarn_export_all]).
 
diff --git a/test/should_pass/tuple_union.erl b/test/should_pass/tuple_union_pass.erl
similarity index 74%
rename from test/should_pass/tuple_union.erl
rename to test/should_pass/tuple_union_pass.erl
index 74693dea..32465eaa 100644
--- a/test/should_pass/tuple_union.erl
+++ b/test/should_pass/tuple_union_pass.erl
@@ -1,4 +1,4 @@
--module(tuple_union).
+-module(tuple_union_pass).
 
 -export([f/0]).
 
diff --git a/test/should_pass/type_refinement.erl b/test/should_pass/type_refinement_pass.erl
similarity index 98%
rename from test/should_pass/type_refinement.erl
rename to test/should_pass/type_refinement_pass.erl
index 83cb578d..c8341709 100644
--- a/test/should_pass/type_refinement.erl
+++ b/test/should_pass/type_refinement_pass.erl
@@ -1,4 +1,4 @@
--module(type_refinement).
+-module(type_refinement_pass).
 
 -compile([export_all, nowarn_export_all]).