contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
    return lock.withLock(action)
  }

  inline fun <T> RealConnection.withLock(action: () -> T): T {
    contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
    return lock.withLock(action)
  }

  inline fun <T> RealCall.withLock(action: () -> T): T {
    contract { callsInPlace(action, InvocationKind.EXACTLY_ONCE) }
    return lock.withLock(action)
  }

	ztunClient := fixture.ztunClient
	uid := fixture.uid

	m, fds := readRequest(t, ztunClient)
	// we got am essage from ztun, so it should have observed us being connected
	mt.Assert(ztunnelConnected.Name(), nil, monitortest.Exactly(1))

	// we should get the fd to dev null. note that we can't assert the fd number
	// as the kernel may have given us a different number that refers to the same file.
	assert.Equal(t, len(fds), 1)

		if len(e.SFunc.ArgsList) != 2 {
			return qProp{err: fmt.Errorf("%s needs exactly 2 arguments", string(funcName))}
		}
		for _, arg := range e.SFunc.ArgsList {
			result.combine(arg.analyze(s))
		}
		return result

	case sqlFnCharLength, sqlFnCharacterLength:
		if len(e.SFunc.ArgsList) != 1 {
			return qProp{err: fmt.Errorf("%s needs exactly 2 arguments", string(funcName))}
		}
		for _, arg := range e.SFunc.ArgsList {

        "network interceptor ${interceptors[index - 1]} must retain the same host and port"
      }
      check(calls == 1) {
        "network interceptor ${interceptors[index - 1]} must call proceed() exactly once"
      }
    }

    // Call the next interceptor in the chain.
    val next = copy(index = index + 1, request = request)
    val interceptor = interceptors[index]

    @Suppress("USELESS_ELVIS")

   * @throws IllegalArgumentException if the stream consists of two or more elements.
   * @throws NullPointerException if any element in the stream is {@code null}.
   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be
   *     {@code null}) and returns {@code Optional.empty()} if it has none.
   */
  @SuppressWarnings("unchecked")
  public static <T> Collector<T, ?, Optional<T>> toOptional() {

   */
  protected final void expectContents(E... elements) {
    expectContents(Arrays.asList(elements));
  }

  /**
   * Asserts that the collection under test contains exactly the given elements, respecting
   * cardinality but not order. Subclasses may override this method to provide stronger assertions,
   * e.g., to check ordering in lists, but realize that <strong>unless a test extends {@link

You could want to set up a different database for testing, rollback the data after the tests, pre-fill it with some testing data, etc.

The main idea is exactly the same you saw in that previous chapter.

## Add tests for the SQL app

Let's update the example from [SQL (Relational) Databases](../tutorial/sql-databases.md){.internal-link target=_blank} to use a testing database.

package lifecycle

import (
	"encoding/xml"
	"io"

	"github.com/minio/minio-go/v7/pkg/tags"
)

var errInvalidFilter = Errorf("Filter must have exactly one of Prefix, Tag, or And specified")

// Filter - a filter for a lifecycle configuration Rule.
type Filter struct {
	XMLName xml.Name `xml:"Filter"`
	set     bool

	Prefix Prefix

					return a.Name
				})
				return makePodLabelMap(havePods)
			}, tt.wantLabels)
			if tt.wantCount > 0 {
				mt.Assert(podsRepaired.Name(), tt.wantTags, monitortest.Exactly(tt.wantCount))
			}
		})
	}
}

func TestDeletePods(t *testing.T) {
	tests := []struct {
		name      string
		client    kube.Client
		config    config.RepairConfig
		wantErr   bool

   */
  protected final void expectContents(E... elements) {
    expectContents(Arrays.asList(elements));
  }

  /**
   * Asserts that the collection under test contains exactly the given elements, respecting
   * cardinality but not order. Subclasses may override this method to provide stronger assertions,
   * e.g., to check ordering in lists, but realize that <strong>unless a test extends {@link