testsuite/synth: add more tests for subtraction in std_logic_unsigned

1 files changed, 20 insertions, 0 deletions

diff --git a/testsuite/synth/issue1951/tb_sub01.vhdl b/testsuite/synth/issue1951/tb_sub01.vhdl
new file mode 100644
index 000000000..f47abe5de
--- /dev/null
+++ b/testsuite/synth/issue1951/tb_sub01.vhdl
@@ -0,0 +1,20 @@
+entity tb_sub01 is
+end tb_sub01;
+
+library ieee;
+use ieee.std_logic_1164.all;
+
+architecture behav of tb_sub01 is
+  signal i, o : std_logic_vector(3 downto 0) := x"0";
+begin
+  dut: entity work.sub01
+    port map (i => i, o => o);
+
+  process
+  begin
+    i <= x"0";
+    wait for 1 ns;
+    assert o = x"1" severity failure;
+    wait;
+  end process;
+end behav;