src/main/java/org/fest/assertions/api/StringAssert.java
public @Nonnull
  StringAssert contains(@Nonnull String sequence) {
    strings.assertContains(description, actual, sequence);
    return this;
  }
public @Nonnull
  StringAssert contains(@Nonnull String sequence) {
    strings.assertContains(description, actual, sequence);
    return this;
  }
Verifies that the <em>actual</em> {@code String} contains the given sequence.

@param sequence the sequence to look for.
@return {@code this} assertion object.
@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 one.