Merge pull request #33

Added optionalOf methods to AbstractValueProvider

.gitignore

@@ -1,5 +1,6 @@
 .gradle
 .idea
+.vscode
 *.log
 **/build/
 jgiven-reports

core/src/main/java/com/tngtech/valueprovider/AbstractValueProvider.java

@@ -16,9 +16,11 @@
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.UUID;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
@@ -1018,6 +1020,49 @@ public boolean booleanValue() {
         return random.nextBoolean();
     }
 
+    /**
+     * <p>
+     * Generates an {@link Optional} of {@code <T>} by means of {@code generator}.
+     * Example:
+     * <pre>
+     * static class MyBeanTestData {
+     *     public static MyBean myBean(ValueProvider valueProvider) {
+     *         // builds and returns your bean
+     *     }
+     * }
+     *
+     * ValueProvider vp = ValueProviderFactory.createRandomValueProvider();
+     * vp.optionalOf(MyBeanTestData::myBean);
+     * vp.optionalOf(provider -> provider.randomString(10));
+     * </pre>
+     * </p>
+     *
+     * @param <T> the type of value to generate
+     * @param generator a generator {@link Function} to generate {@code <T>} given an implementation of {@link AbstractValueProvider}.
+     * @return the generated {@link Optional}.
+     */
+    public <T> Optional<T> optionalOf(Function<VP, T> generator) {
+        return booleanValue() ? Optional.of(generator.apply((VP) this)) : Optional.empty();
+    }
+
+    /**
+     * <p>
+     * Generates an {@link Optional} of {@code <T>} by means of {@code supplier}.
+     * Example:
+     * <pre>
+     * ValueProvider vp = ValueProviderFactory.createRandomValueProvider();
+     * vp.optionalOf(vp::uuid);
+     * </pre>
+     * </p>
+     *
+     * @param <T> the type of value to generate
+     * @param supplier a supplier {@link Supplier} to generate {@code <T>}.
+     * @return the generated {@link Optional}.
+     */
+    public <T> Optional<T> optionalOf(Supplier<T> supplier) {
+        return booleanValue() ? Optional.of(supplier.get()) : Optional.empty();
+    }
+
     /**
      * Generates an IPv4 or IPv6 address.
      *

core/src/test/java/com/tngtech/valueprovider/ValueProviderTest.java

@@ -203,6 +203,40 @@ void booleanValue_should_create_both_values() {
         assertThat(falseCreated).as("false created").isTrue();
     }
 
+    @Test
+    void optionalOf_on_function_should_create_present_and_empty() {
+        ValueProvider random = withRandomValues();
+
+        boolean presentCreated = false;
+        boolean emptyCreated = false;
+        for (int i = 0; i < 1000 && !(presentCreated && emptyCreated); i++) {
+            if (random.optionalOf(vp -> vp.randomString(10)).isPresent()) {
+                presentCreated = true;
+            } else {
+                emptyCreated = true;
+            }
+        }
+        assertThat(presentCreated).as("present created").isTrue();
+        assertThat(emptyCreated).as("empty created").isTrue();
+    }
+
+    @Test
+    void optionalOf_on_supplier_should_create_present_and_empty() {
+        ValueProvider random = withRandomValues();
+
+        boolean presentCreated = false;
+        boolean emptyCreated = false;
+        for (int i = 0; i < 1000 && !(presentCreated && emptyCreated); i++) {
+            if (random.optionalOf(random::uuid).isPresent()) {
+                presentCreated = true;
+            } else {
+                emptyCreated = true;
+            }
+        }
+        assertThat(presentCreated).as("present created").isTrue();
+        assertThat(emptyCreated).as("empty created").isTrue();
+    }
+
     @Test
     void intNumber_should_create_number_between_min_and_max() {
         for (int i = 0; i < 1000; i++) {