mockit.Expectations Maven / Gradle / Ivy

/*
 * Copyright (c) 2006 JMockit developers
 * This file is subject to the terms of the MIT license (see LICENSE.txt).
 */
package mockit;

import java.util.*;
import javax.annotation.*;

import mockit.internal.expectations.*;

/**
 * Used to record expectations on {@linkplain Mocked mocked} types and their instances.
 * 
 * Each recorded expectation is intended to match one or more method or constructor invocations, that we expect will occur during the execution of
 * code under test.
 * When a match is detected, the recorded {@linkplain #result result} is returned to the caller.
 * Alternatively, a recorded exception/error is thrown, or an arbitrary {@linkplain Delegate delegate} method is executed.
 * 

 * Expectations are recorded simply by invoking the desired method or constructor on the mocked type/instance, during the initialization of an
 * Expectations object.
 * This is done by instantiating an anonymous subclass containing an instance initialization body, or as we call it, an expectation block:
 * 
 * // Record one or more expectations on available mocked types/instances.
 * new Expectations() {{
 *    mock1.expectedMethod(anyInt); result = 123; times = 2;
 *    mock2.anotherExpectedMethod(1, "test"); result = "Abc";
 * }};
 *
 * // Exercise tested code, with previously recorded expectations now available for replay.
 * codeUnderTest.doSomething();
 * 
 * During replay, invocations matching a recorded expectation must occur at least once (unless specified otherwise);
 * if, by the end of the test, no matching invocation occurred for a given recorded expectation, the test will fail with a
 * MissingInvocation error.
 * 
 * When multiple expectations are recorded, matching invocations are allowed to occur in a different order.
 * So, the order in which expectations are recorded is not significant.
 * 

 * Besides the special {@link #result} field already mentioned, there are several other fields and methods which can be used inside the
 * expectation block:
 * a) {@link #returns(Object, Object, Object...)}, a convenience method for returning a sequence of values;
 * b) argument matchers such as {@link #anyInt}, {@link #anyString}, {@link #withNotNull()}, etc., which relax or constrain the matching of
 * argument values;
 * c) the {@link #times}, {@link #minTimes}, and {@link #maxTimes} fields, which relax or constrain the expected and/or allowed number of matching
 * invocations.
 * 

 * By default, the exact instance on which instance method invocations will occur during replay is not verified to be the same as the
 * instance used when recording the expectation.
 * That said, instance-specific matching can be obtained by declaring the mocked type as {@linkplain Injectable @Injectable}, or by declaring
 * multiple mock fields and/or mock parameters of the same mocked type (so that separate expectations can be recorded for each mock instance).
 * 

 * Invocations occurring during replay, whether they matched recorded expectations or not, can be explicitly verified after exercising the
 * code under test.
 * To that end, we use a set of complementary base classes: {@link Verifications}, {@link VerificationsInOrder}, and {@link FullVerifications}.
 * Similar to expectation blocks, these classes allow us to create verification blocks.
 *
 * @see #Expectations()
 * @see #Expectations(Object...)
 * @see Tutorial
 */
public class Expectations extends Invocations
{
   /**
    * A value assigned to this field will be taken as the result for the expectation that is being recorded.
    * 

    * If the value is a {@link Throwable} then it will be thrown when a matching invocation later occurs.
    * Otherwise, it's assumed to be a return value for a non-void method, and will be returned from a matching
    * invocation.
    * 

    * If no result is recorded for a given expectation, then all matching invocations will return the appropriate default value according
    * to the method return type:
    * 

    * Most java.lang types (String, Object, etc.): returns null.
    * java.math types (BigDecimal, etc.): returns null.
    * Primitive/wrapper types: returns the standard default value (false for boolean/Boolean, 0 for
    * int/Integer, and so on).
    * 
    * java.util.List, java.util.Collection, or java.lang.Iterable: returns
    * {@link Collections#EMPTY_LIST}.
    * java.util.Iterator or java.util.ListIterator: returns an empty iterator.
    * java.util.Set: returns {@link Collections#EMPTY_SET}.
    * java.util.SortedSet: returns an unmodifiable empty sorted set.
    * java.util.Map: returns {@link Collections#EMPTY_MAP}.
    * java.util.SortedMap: returns an unmodifiable empty sorted map.
    * java.util.Optional: returns {@link Optional#empty()}.
    * Other reference types: returns a mocked instance through cascading.
    * Array types: returns an array with zero elements (empty) in each dimension.
    * 
    * 
    * When an expectation is recorded for a method which actually returns an exception or error (as opposed to throwing
    * one), then the {@link #returns(Object, Object, Object...)} method should be used instead, as it only applies to return values.
    * 

    * Assigning a value whose type differs from the method return type will cause an IllegalArgumentException to be thrown, unless
    * it can be safely converted to the return type.
    * One such conversion is from an array to a collection or iterator.
    * Another is from an array of at least two dimensions to a map, with the first dimension providing the keys and the second the values.
    * Yet another conversion is from a single value to a container type holding that value.
    * 

    * A sequence of consecutive results can be recorded simply by assigning the field multiple times for the same expectation.
    * Alternatively, the desired sequence of results for a single-valued return type can be recorded by assigning an array, an
    * {@link Iterable}, or an {@link Iterator} containing the individual results in order.
    * 

    * Results that depend on some programming logic can be provided through a {@linkplain Delegate} object assigned to the field.
    * This applies to void and non-void methods, as well as to constructors.
    * 

    * Finally, when recording an expectation on a constructor of a mocked class, an arbitrary instance of said class can be
    * assigned to the field.
    * In this case, additional expectations recorded or verified on the assigned instance will also match invocations to instance methods
    * made on future instances, provided they get created through a matching constructor invocation.
    *
    * @see #returns(Object, Object, Object...)
    * @see Tutorial
    */
   @Nullable
   protected Object result;

   /**
    * Registers one or more expectations recorded on available mocked types and/or mocked instances, as written inside the instance
    * initialization body of an anonymous subclass.
    *
    * @see #Expectations(Object...)
    * @see Tutorial
    */
   protected Expectations() {
      RecordAndReplayExecution execution = new RecordAndReplayExecution(this, (Object[]) null);
      //noinspection ConstantConditions
      currentPhase = execution.getRecordPhase();
   }

   /**
    * Same as {@link #Expectations()}, except that one or more classes will be partially mocked according to the expectations recorded in the
    * expectation block.
    * 

    * The classes to be partially mocked are those directly specified through their Class objects as well as those to which any given
    * objects belong.
    * During replay, any invocations to one of these classes or objects will execute real production code, unless a matching expectation was
    * recorded.
    * This mechanism, however, does not apply to native methods, which are not supported for partial mocking.
    * 

    * For a given Class object, all constructors and methods can be mocked, from the specified class up to but not including
    * java.lang.Object.
    * For a given object, only methods can be mocked, not constructors; also, during replay, invocations to instance methods will only
    * match expectations recorded on the given instance (or instances, if more than one was given).
    *
    * @param classesOrObjectsToBePartiallyMocked one or more classes or objects whose classes are to be partially mocked
    *
    * @throws IllegalArgumentException if given a Class object for an interface, an annotation, an array, a primitive/wrapper type, a
    * synthetic class, a {@linkplain java.lang.reflect.Proxy#isProxyClass(Class) proxy class}, or if given a value/instance of such a type
    * 
    * @see Tutorial
    */
   protected Expectations(@Nonnull Object... classesOrObjectsToBePartiallyMocked) {
      RecordAndReplayExecution execution = new RecordAndReplayExecution(this, classesOrObjectsToBePartiallyMocked);
      //noinspection ConstantConditions
      currentPhase = execution.getRecordPhase();
   }

   /**
    * Specifies that the previously recorded method invocation will return a given sequence of values during replay.
    * 

    * Calling this method is equivalent to assigning the {@link #result} field two or more times in sequence, or assigning it a single time
    * with an array or iterable containing the same sequence of values.
    * 

    * Certain data conversions will be applied, depending on the return type of the recorded method:
    * 

    * If the return type is iterable and can receive a {@link List} value, then the given sequence of values will be converted into an
    * ArrayList; this list will then be returned by matching invocations at replay time.
    * If the return type is SortedSet or a sub-type, then the given sequence of values will be converted into a
    * TreeSet; otherwise, if it is Set or a sub-type, then a LinkedHashSet will be created to hold the values;
    * the set will then be returned by matching invocations at replay time.
    * If the return type is Iterator or a sub-type, then the given sequence of values will be converted into a List
    * and the iterator created from this list will be returned by matching invocations at replay time.
    * If the return type is an array, then the given sequence of values will be converted to an array of the same type, which will be
    * returned by matching invocations at replay time.
    * 
    * The current expectation will have its upper invocation count automatically set to the total number of values specified to be returned.
    * This upper limit can be overridden through the maxTimes field, if necessary.
    *
    * @param firstValue the first value to be returned at replay time
    * @param secondValue the second value to be returned at replay time
    * @param remainingValues any remaining values to be returned, in the same order
    *
    * @see Tutorial
    */
   protected final void returns(@Nullable Object firstValue, @Nullable Object secondValue, @Nonnull Object... remainingValues) {
      int n = remainingValues.length;
      Object[] values = new Object[2 + n];
      values[0] = firstValue;
      values[1] = secondValue;
      System.arraycopy(remainingValues, 0, values, 2, n);

      ((RecordPhase) currentPhase).addSequenceOfReturnValues(values);
   }
}