diff --git a/app/src/test/java/de/uni_marburg/powersort/FinnSort/FasterFinnSortMockitoTest.java b/app/src/test/java/de/uni_marburg/powersort/FinnSort/FasterFinnSortMockitoTest.java
new file mode 100644
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--- /dev/null
+++ b/app/src/test/java/de/uni_marburg/powersort/FinnSort/FasterFinnSortMockitoTest.java
@@ -0,0 +1,58 @@
+package de.uni_marburg.powersort.FinnSort;
+
+import de.uni_marburg.powersort.JUnitUtil;
+import de.uni_marburg.powersort.benchmark.NaturalOrder;
+import org.junit.jupiter.api.RepeatedTest;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.converter.ConvertWith;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.*;
+import static org.mockito.Mockito.*;
+
+public class FasterFinnSortMockitoTest {
+    @ParameterizedTest
+    @CsvSource({
+            "4|5|6|1|2|3",
+            "100|10|11|1|2|3",
+            "100|11|10|3|2|1",
+            "24|25|26|27|28|21|22|23|18|19|20|4|5|6|7|8|9|10|11|12|13|14|15|16|17|3|1|2",
+    })
+    void foo(@ConvertWith(JUnitUtil.IntegerArrayConverter.class) Integer[] a) {
+        printPowers(a);
+    }
+
+    void printPowers(Object[] a) {
+        FasterFinnSort<Object> ffs = new FasterFinnSort<>(a, NaturalOrder.INSTANCE, null, 0, 0);
+        FasterFinnSort<Object> spiedFfs = spy(ffs);
+
+        // Don't extend short runs with `binarySort()`
+        when(spiedFfs.minRunLength(anyInt())).thenReturn(0);
+
+        // Capture calculated power values.
+        final ResultCaptor<Integer> resultCaptor = new ResultCaptor<>();
+        doAnswer(resultCaptor).when(spiedFfs).power(anyInt(), anyInt());
+
+
+        sort(a, spiedFfs);
+
+
+        List<Integer> calculatedPowers = resultCaptor.getAllValues();
+        System.out.println(Arrays.toString(calculatedPowers.toArray()));
+    }
+
+    /**
+     * Sorts the given array using FasterFinnSort.
+     */
+    void sort(Object[] a, FasterFinnSort<Object> ffs) {
+        // Don't sort short array with `binarySort()`
+        boolean forcePowersortShortArray = true;
+
+        FasterFinnSortWrapper.sort(a, 0, a.length, NaturalOrder.INSTANCE, null, 0, 0, ffs, forcePowersortShortArray);
+    }
+}
diff --git a/app/src/test/java/de/uni_marburg/powersort/FinnSort/FasterFinnSortWrapper.java b/app/src/test/java/de/uni_marburg/powersort/FinnSort/FasterFinnSortWrapper.java
new file mode 100644
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--- /dev/null
+++ b/app/src/test/java/de/uni_marburg/powersort/FinnSort/FasterFinnSortWrapper.java
@@ -0,0 +1,66 @@
+package de.uni_marburg.powersort.FinnSort;
+
+import java.util.Comparator;
+
+import static de.uni_marburg.powersort.FinnSort.FasterFinnSort.MIN_MERGE;
+import static de.uni_marburg.powersort.FinnSort.FasterFinnSort.binarySort;
+import static de.uni_marburg.powersort.FinnSort.FasterFinnSort.countRunAndMakeAscending;
+
+public class FasterFinnSortWrapper {
+    /**
+     * Copy of `FasterFinnSort.java`. Param `ts` has been added to allow dependency injection for testing.
+     *
+     * @param ts: If non-null, the creation of `ts` with `new FasterFinnSort<>(a, c, work, workBase, workLen)` in this methods body is skipped. Instead, the given `ts` is used.
+     */
+    public static <T> void sort(T[] a, int lo, int hi, Comparator<? super T> c,
+                                T[] work, int workBase, int workLen,
+                                FasterFinnSort<T> ts, boolean forcePowersortShortArray) {
+        assert c != null && a != null && lo >= 0 && lo <= hi && hi <= a.length;
+
+        int nRemaining = hi - lo;
+        if (nRemaining < 2)
+            return;  // Arrays of size 0 and 1 are always sorted
+
+        // If array is small, do a "mini-TimSort" with no merges
+        if (!forcePowersortShortArray && nRemaining < MIN_MERGE) {
+            int initRunLen = countRunAndMakeAscending(a, lo, hi, c);
+            binarySort(a, lo, hi, lo + initRunLen, c);
+            return;
+        }
+
+        /*
+         * March over the array once, left to right, finding natural runs,
+         * extending short natural runs to minRun elements, and merging runs
+         * to maintain stack invariant.
+         */
+        if (ts == null) ts = new FasterFinnSort<>(a, c, work, workBase, workLen);
+        int minRun = ts.minRunLength(nRemaining);
+        System.out.println("minRun: " + minRun);
+        do {
+            // Identify next run
+            int runLen = countRunAndMakeAscending(a, lo, hi, c);
+            System.out.println("runLen: " + runLen);
+
+            // If run is short, extend to min(minRun, nRemaining)
+            if (runLen < minRun) {
+                System.out.println("Extend run of length " + runLen + " to " + Math.min(minRun, nRemaining));
+                int force = nRemaining <= minRun ? nRemaining : minRun;
+                binarySort(a, lo, lo + force, lo + runLen, c);
+                runLen = force;
+            }
+
+            // Push run onto pending-run stack, and maybe merge
+            ts.pushRun(lo, runLen, hi - lo);
+            ts.mergeCollapse();
+
+            // Advance to find next run
+            lo += runLen;
+            nRemaining -= runLen;
+        } while (nRemaining != 0);
+
+        // Merge all remaining runs to complete sort
+        assert lo == hi;
+        ts.mergeForceCollapse();
+        assert ts.stackSize == 1;
+    }
+}
diff --git a/app/src/test/java/de/uni_marburg/powersort/FinnSort/ResultCaptor.java b/app/src/test/java/de/uni_marburg/powersort/FinnSort/ResultCaptor.java
new file mode 100644
index 0000000..05ca6d7
--- /dev/null
+++ b/app/src/test/java/de/uni_marburg/powersort/FinnSort/ResultCaptor.java
@@ -0,0 +1,31 @@
+package de.uni_marburg.powersort.FinnSort;
+
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+
+import java.util.ArrayList;
+import java.util.List;
+
+
+/**
+ * Source: https://stackoverflow.com/a/25694142/6334421
+ * <p>
+ * Alternative which didn't work: https://github.com/mockito/mockito/issues/2422
+ */
+public class ResultCaptor<T> implements Answer {
+    private final List<T> results = new ArrayList<>();
+
+    /**
+     * Returns all captured values.
+     */
+    public List<T> getAllValues() {
+        return results;
+    }
+
+    @Override
+    public T answer(InvocationOnMock invocationOnMock) throws Throwable {
+        T result = (T) invocationOnMock.callRealMethod();
+        results.add(result);
+        return result;
+    }
+}