Assert a std::fs::read_to_string(path) contains a pattern.
Pseudocode: std::fs::read_to_string(path) contains expr
let path = "alfa.txt"; let containee = "alfa"; assert_fs_read_to_string_contains!(&path, &containee);
assert_fs_read_to_string_contains
assert_fs_read_to_string_contains_as_result
debug_assert_fs_read_to_string_contains