code: public void toStartWith(String start) {
  		Arguments.ensureNotNull(start, "start cannot be null");
  		expectNotNull(this.getValue(), "Expected null to start with '%s'", start);
  		expectTrue(this.getValue().startsWith(start), "Expected '%s' to start with '%s'", this.getValue(), start);
  	}
docs: Checks if the stored {@code String} starts with a given sub string.
  <p>This method throws an {@code AssertionError} if
  <ul>
  <li>the stored {@code String} does not start with {@code start}</li>
  <li>the stored {@code String} is {@code null}</li>
  </ul>
  @throws java.lang.IllegalArgumentException if {@code start} is {@code null}.
  @param start the sub string