gtkwave does not run for the expected time within a testbench

When I run python run.py -g I am expecting to see the output of my unit test displayed within gtkwave.

Test Bench

LIBRARY vunit_lib;
CONTEXT vunit_lib.vunit_context;

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

LIBRARY src;
USE src.mux_2i_1o;

ENTITY tb_mux_2i_1o IS
  GENERIC (runner_cfg : STRING);
END ENTITY;

ARCHITECTURE tb OF tb_mux_2i_1o IS
  SIGNAL button : std_logic := 'X';
  SIGNAL input_1 : std_logic := '0';
  SIGNAL input_2 : std_logic := '1';
  SIGNAL output : std_logic;
BEGIN
  mux : ENTITY mux_2i_1o PORT MAP (
    button => button,
    input_1 => input_1,
    input_2 => input_2,
    output => output
    );

  main : PROCESS
  BEGIN
    test_runner_setup(runner, runner_cfg);

    WHILE test_suite LOOP

      IF run("button press to switch inputs") THEN
        button <= '0';
        check(output = input_1);
        wait for 20 ns;
        button <= '1';
        wait for 20 ns;
        check(output = input_2, "Input did not change when button was pressed");
      END IF;

    END LOOP;

    test_runner_cleanup(runner); -- Simulation ends here
    WAIT;
  END PROCESS;
END ARCHITECTURE;

As you can see, there are two 20ns waits within the test bench. Which means I am expecting the gtkwave gui to show me a sim for a total of 40ns. But when I run python run.py -g I get the following output.

Steps to reproduce on Linux desktop environment

cd $HOME
git clone https://github.com/seanybaggins/ben_eaters_8_bit_computer.git
cd ben_eaters_8_bit_computer

docker run --volume="$HOME/.Xauthority:/root/.Xauthority:rw" --volume="$HOME/ben_eaters_8_bit_computer/:$HOME/ben_eaters_8_bit_computer" -w="$HOME/ben_eaters_8_bit_computer"  --env="DISPLAY" --net=host ghdl/ext python run.py -g

docker start -a <default name>

ghdl / docker

gtkwave does not run for the expected time within a testbench #26