testPropertiesUpheld

fn testPropertiesUpheld(_: void, smith: *std.testing.Smith) !void {
    @disableInstrumentation();
    var source_buf: [512]u8 = undefined;
    const len = smith.sliceWeightedBytes(source_buf[0 .. source_buf.len - 1], &.{
        .rangeAtMost(u8, 0x00, 0xff, 1),
        .rangeAtMost(u8, 0x20, 0x7e, 4),
        .rangeAtMost(u8, 0x00, 0x1f, 1),
        .value(u8, 0, 6),
        .value(u8, ' ', 6),
        .rangeAtMost(u8, '\t', '\n', 6), // \t, \n
        .value(u8, '\r', 3),
    });
    source_buf[len] = 0;
    const source = source_buf[0..len :0];

    var tokenizer = Tokenizer.init(source);
    var tokenization_failed = false;
    while (true) {
        const token = tokenizer.next();

        // Property: token end location after start location (or equal)
        try std.testing.expect(token.loc.end >= token.loc.start);

        switch (token.tag) {
            .invalid => {
                tokenization_failed = true;

                // Property: invalid token always ends at newline or eof
                try std.testing.expect(source[token.loc.end] == '\n' or source[token.loc.end] == 0);
            },
            .eof => {
                // Property: EOF token is always 0-length at end of source.
                try std.testing.expectEqual(source.len, token.loc.start);
                try std.testing.expectEqual(source.len, token.loc.end);
                break;
            },
            else => continue,
        }
    }

    if (tokenization_failed) return;
    for (source) |cur| {
        // Property: No null byte allowed except at end.
        if (cur == 0) {
            return error.TestUnexpectedResult;
        }
        // Property: No ASCII control characters other than \n, \t, and \r are allowed.
        if (std.ascii.isControl(cur) and cur != '\n' and cur != '\t' and cur != '\r') {
            return error.TestUnexpectedResult;
        }
    }
}