restructure testbenches and common code

src/bh_assert.sv

@@ -1,48 +0,0 @@
-
-int bh_assert_pass_count = 0;
-int bh_assert_fail_count = 0;
-
-logic bh_info_enable = 0;
-
-function logic bh_assert_equal(int val, int expected, string description);
-    // display results
-    $timeformat(-9, 2, " ns", 20);
-    $display(
-        "%t: %s: %d %s %d - %s",
-        $time,
-        val == expected ? "PASS" : "FAIL",
-        val,
-        val == expected ? "==" : "!=",
-        expected,
-        description
-    );
-
-    // update statistics
-    if (val == expected) begin
-        bh_assert_pass_count = bh_assert_pass_count + 1;
-    end else begin
-        bh_assert_fail_count = bh_assert_fail_count + 1;
-    end
-
-    return val == expected; 
-endfunction
-
-function void bh_assert_stats();
-    $timeformat(-9, 2, " ns", 20);
-    $display("%t: DONE: ");
-    if (bh_assert_pass_count + bh_assert_fail_count == 0) begin
-        $display("ERROR: no assertions found");
-        // TODO: error in a better way?
-    end else if (bh_assert_fail_count > 0) begin
-        $display("ERROR: some tests failed");
-    end else begin
-        $display("SUCCESS: all tests passed");
-    end
-endfunction
-
-function void bh_info(string description);
-    if (bh_info_enable) begin
-        $display(description);
-    end
-endfunction
-