fix: create subclass of collection as proxy

This is necessary, because Fixture cannot create instances of non-
vanilla collections.

Refs: #114

Author: Nylle

src/main/java/com/github/nylle/javafixture/SpecimenType.java

@@ -12,10 +12,27 @@
 import java.time.temporal.Temporal;
 import java.time.temporal.TemporalAdjuster;
 import java.time.temporal.TemporalAmount;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Deque;
+import java.util.EnumSet;
+import java.util.HashSet;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.NavigableSet;
 import java.util.Objects;
+import java.util.Queue;
+import java.util.Set;
+import java.util.SortedSet;
+import java.util.TreeSet;
+import java.util.concurrent.BlockingDeque;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingDeque;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.LinkedTransferQueue;
+import java.util.concurrent.TransferQueue;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
@@ -138,7 +155,30 @@ public boolean isParameterized() {
     }
 
     public boolean isCollection() {
-        return Collection.class.isAssignableFrom(asClass());
+        if(!isInterface() && !isAbstract()) {
+            return Collection.class.isAssignableFrom(asClass());
+        }
+
+        return Stream.of(Collection.class,
+                        List.class,
+                        NavigableSet.class,
+                        SortedSet.class,
+                        Set.class,
+                        EnumSet.class,
+                        Deque.class,
+                        BlockingDeque.class,
+                        Queue.class,
+                        BlockingQueue.class,
+                        TransferQueue.class,
+                        ArrayList.class,
+                        HashSet.class,
+                        TreeSet.class,
+                        ArrayDeque.class,
+                        LinkedBlockingDeque.class,
+                        LinkedList.class,
+                        LinkedBlockingQueue.class,
+                        LinkedTransferQueue.class)
+                .anyMatch(x -> asClass().isAssignableFrom(x));
     }
 
     public boolean isMap() {

src/test/java/com/github/nylle/javafixture/FixtureTest.java

@@ -2,6 +2,7 @@
 
 import com.github.nylle.javafixture.testobjects.ITestGeneric;
 import com.github.nylle.javafixture.testobjects.ITestGenericInside;
+import com.github.nylle.javafixture.testobjects.TestCollectionExtension;
 import com.github.nylle.javafixture.testobjects.TestEnum;
 import com.github.nylle.javafixture.testobjects.TestObject;
 import com.github.nylle.javafixture.testobjects.TestObjectGeneric;
@@ -26,6 +27,8 @@
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
+import javassist.util.proxy.Proxy;
+
 import java.io.File;
 import java.time.Instant;
 import java.time.LocalDate;
@@ -570,6 +573,16 @@ void createExceptionWithLimitedTree() {
                 .doesNotThrowAnyException();
     }
 
+    @Test
+    void createSubclassOfCollectionAsProxyBecauseFixtureCannotCreateAnInstanceOfANonVanillaCollection() {
+        var sut = new Fixture(configuration);
+
+        var result = sut.create(new SpecimenType<TestCollectionExtension<String>>() {});
+
+        assertThat(result).isInstanceOf(TestCollectionExtension.class);
+        assertThat(Proxy.class.isAssignableFrom(result.getClass())).isTrue();
+    }
+
     private Stream<Throwable> flattenRecursively(Throwable throwable) {
         return Stream.of(throwable.getSuppressed()).flatMap(x -> flattenRecursively(x));
     }

src/test/java/com/github/nylle/javafixture/SpecimenTypeTest.java

@@ -6,6 +6,7 @@
 import com.github.nylle.javafixture.testobjects.ClassWithBuilder;
 import com.github.nylle.javafixture.testobjects.ITestGeneric;
 import com.github.nylle.javafixture.testobjects.TestAbstractClass;
+import com.github.nylle.javafixture.testobjects.TestCollectionExtension;
 import com.github.nylle.javafixture.testobjects.TestEnum;
 import com.github.nylle.javafixture.testobjects.TestObject;
 import com.github.nylle.javafixture.testobjects.TestObjectGeneric;
@@ -111,6 +112,7 @@ void isCollection() {
         assertThat(new SpecimenType<LinkedList<String>>() {}.isCollection()).isTrue();
         assertThat(new SpecimenType<LinkedBlockingQueue<String>>() {}.isCollection()).isTrue();
         assertThat(new SpecimenType<LinkedTransferQueue<String>>() {}.isCollection()).isTrue();
+        assertThat(new SpecimenType<TestCollectionExtension<String>>() {}.isCollection()).isFalse();
     }
 
     @TestWithCases

src/test/java/com/github/nylle/javafixture/testobjects/TestCollectionExtension.java

@@ -0,0 +1,7 @@
+package com.github.nylle.javafixture.testobjects;
+
+import java.util.Collection;
+
+public interface TestCollectionExtension<T> extends Collection<T> {
+    int customMethod();
+}