src/main/java/org/fest/assertions/internal/Strings.java
public void assertContains(@Nullable Description description, @Nullable String actual, @Nonnull String sequence) {
    checkNotNull(sequence);
    assertNotNull(description, actual);
    if (!actual.contains(sequence)) {
      String format = "expecting:<%s> to contain:<%s>";
      throw failures.failure(description, new BasicErrorMessageFactory(format, actual, sequence));
    }
  }
public void assertContains(@Nullable Description description, @Nullable String actual, @Nonnull String sequence) {
    checkNotNull(sequence);
    assertNotNull(description, actual);
    if (!actual.contains(sequence)) {
      String format = "expecting:<%s> to contain:<%s>";
      throw failures.failure(description, new BasicErrorMessageFactory(format, actual, sequence));
    }
  }
Verifies that the <em>actual</em> {@code String} contains the given sequence.

@param description the description of the <em>actual</em> {@code String}.
@param actual the <em>actual</em> {@code String}.
@param sequence the sequence to look for.
@throws NullPointerException if the given sequence is {@code null}.
@throws AssertionError if the <em>actual</em> {@code String} is {@code null}.
@throws AssertionError if the <em>actual</em> {@code String} does not contain the given sequence.