src/main/java/org/fest/assertions/internal/Maps.java
public <K> void assertDoesNotContainKey(Description description, Map<?, ?> actual, K key) {
    assertNotNull(description, actual);
    if (actual.containsKey(key)) {
      throw failures.failure(description, shouldNotContainKey(actual, key));
    }
  }
public <K> void assertDoesNotContainKey(Description description, Map<?, ?> actual, K key) {
    assertNotNull(description, actual);
    if (actual.containsKey(key)) {
      throw failures.failure(description, shouldNotContainKey(actual, key));
    }
  }
Asserts that the actual map not contains the given key.

@param description contains information about the assertion.
@param actual the given {@code Map}.
@param key the given key
@throws AssertionError if the actual map is {@code null}.
@throws AssertionError if the actual map contains the given key.