src/main/java/org/fest/assertions/internal/Maps.java
public <K, V> void assertDoesNotContainDuplicateValues(Description description, Map<K, V> actual) {
    assertNotNull(description, actual);
    Collection<?> duplicates = duplicatesFrom(actual.values());
    if (!duplicates.isEmpty()) {
      throw failures.failure(description, shouldNotHaveDuplicates(actual, duplicates));
    }
  }
public <K, V> void assertDoesNotContainDuplicateValues(Description description, Map<K, V> actual) {
    assertNotNull(description, actual);
    Collection<?> duplicates = duplicatesFrom(actual.values());
    if (!duplicates.isEmpty()) {
      throw failures.failure(description, shouldNotHaveDuplicates(actual, duplicates));
    }
  }
Asserts that the actual map does not contain the duplicate values.

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