Make sure you create a [virtual environment](../virtual-environments.md){.internal-link target=_blank}, activate it, and then install it, for example:

```console
$ pip install httpx
```

///

Import `TestClient`.

Create a `TestClient` by passing your **FastAPI** application to it.

	// Gatherers for non-bucket MetricsGroup's
	mgGatherers map[collectorPath]prometheus.Gatherer

	collectorPaths []collectorPath
}

func newMetricGroups(r *prometheus.Registry) *metricsV3Collection {
	// Create all metric groups.
	apiRequestsMG := NewMetricsGroup(apiRequestsCollectorPath,
		[]MetricDescriptor{
			apiRejectedAuthTotalMD,
			apiRejectedHeaderTotalMD,
			apiRejectedTimestampTotalMD,
			apiRejectedInvalidTotalMD,

        .addEqualityGroup(
            getMultiset(), getSubjectGenerator().create(getSampleElements().toArray()))
        .testEquals();
  }

  @CollectionSize.Require(absent = ZERO)
  public void testNotEqualsEmpty() {
    new EqualsTester()
        .addEqualityGroup(getMultiset())
        .addEqualityGroup(getSubjectGenerator().create())
        .testEquals();
  }

  public void testHashCodeMatchesEntrySet() {

    return orderEntriesByKey(insertionOrder);
  }

  @Override
  protected abstract SortedMap<String, String> create(Entry<String, String>[] entries);

  @Override
  public SortedMap<String, String> create(Object... entries) {
    return (SortedMap<String, String>) super.create(entries);
  }

    return new Enums();
  }

  @Override
  public Set<AnEnum> create(Object... elements) {
    AnEnum[] array = new AnEnum[elements.length];
    int i = 0;
    for (Object e : elements) {
      array[i++] = (AnEnum) e;
    }
    return create(array);
  }

  protected abstract Set<AnEnum> create(AnEnum[] elements);

  @Override
  public AnEnum[] createArray(int length) {

    return orderEntriesByKey(insertionOrder);
  }

  @Override
  protected abstract SortedMap<String, String> create(Entry<String, String>[] entries);

  @Override
  public SortedMap<String, String> create(Object... entries) {
    return (SortedMap<String, String>) super.create(entries);
  }

 * Immutable empty instances are returned for collection types; {@code ""} for string; {@code 0} for
 * number types; reasonable default instance for other stateless types. For mutable types, a fresh
 * instance is created each time {@code get()} is called.
 *
 * @author Kevin Bourrillion
 * @author Ben Yu
 * @since 12.0
 */
@GwtIncompatible
@J2ktIncompatible
@NullMarked
public final class ArbitraryInstances {

                                    }
                                }
                            },
                        },
                    },
                    "summary": "Create an item",

    }

    /**
     * Create a test byte array with specified size and pattern
     */
    protected byte[] createTestData(int size) {
        byte[] data = new byte[size];
        for (int i = 0; i < size; i++) {
            data[i] = (byte) (i % 256);
        }
        return data;
    }

    /**
     * Create a test string with specified length
     */

     *
     * @param create file creation time
     * @param lastAccess last access time
     * @param lastWrite last write time
     * @param change last change time
     * @param attributes file attributes
     */
    public FileBasicInfo(final long create, final long lastAccess, final long lastWrite, final long change, final int attributes) {
        this.createTime = create;
        this.lastAccessTime = lastAccess;