test runner automatically handles tests with top-level module inside both inputs

test/basic/enum_tb.v

-// intentionally empty

test/basic/named_block_tb.v

-// intentionally empty

test/basic/package_tb.v

-// intentionally empty

test/basic/packed_array_shadow_tb.v

-// intentionally empty

test/basic/part_select_tb.v

-// intentionally empty

test/basic/struct_shadow_tb.v

-// intentionally empty

test/basic/tf_block_tb.v

-// intentionally empty

test/basic/top_tf_tb.v

-// intentionally empty

test/lex/run.sh

 #!/bin/bash
-NO_SEPARATE_TBS=1
 source ../lib/runner.sh

test/lib/runner.sh

@@ -66,16 +66,18 @@ assertConverts() {
 simpleTest() {
     sv="$1"
     ve="$2"
-    if [ -z ${NO_SEPARATE_TBS} ]; then
-        tb="$3"
-    else
-        tb="$SCRIPT_DIR/empty.v"
-    fi
+    tb="$3"
 
     assertNotNull "SystemVerilog file not specified" $sv
     assertNotNull "Verilog file not specified" $ve
     assertNotNull "Testbench not specified" $tb
 
+    # some tests don't have a separate testbench, instead having the top-level
+    # module defined in both of the input files
+    if [ ! -f "$tb" ]; then
+        tb="$SCRIPT_DIR/empty.v"
+    fi
+
     assertExists $sv
     assertExists $ve
     assertExists $tb