Convert more tests to kotlin.

Resolves #13829

app/src/test/java/org/thoughtcrime/securesms/testutil/SecureRandomTestUtil.java

@@ -1,48 +0,0 @@
-package org.thoughtcrime.securesms.testutil;
-
-import org.mockito.ArgumentCaptor;
-import org.mockito.invocation.InvocationOnMock;
-import org.mockito.stubbing.Answer;
-
-import java.security.SecureRandom;
-
-import static org.junit.Assert.assertEquals;
-import static org.mockito.Mockito.doAnswer;
-import static org.mockito.Mockito.mock;
-
-public final class SecureRandomTestUtil {
-
-  private SecureRandomTestUtil() {
-  }
-
-  /**
-   * Creates a {@link SecureRandom} that returns exactly the {@param returnValue} the first time
-   * its {@link SecureRandom#nextBytes(byte[])}} method is called.
-   * <p>
-   * Any attempt to call with the incorrect length, or a second time will fail.
-   */
-  public static SecureRandom mockRandom(byte[] returnValue) {
-    SecureRandom           mock     = mock(SecureRandom.class);
-    ArgumentCaptor<byte[]> argument = ArgumentCaptor.forClass(byte[].class);
-
-    doAnswer(new Answer<Void>() {
-
-      private int count;
-
-      @Override
-      public Void answer(InvocationOnMock invocation) {
-        assertEquals("SecureRandom Mock: nextBytes only expected to be called once", 1, ++count);
-
-        byte[] output = argument.getValue();
-
-        assertEquals("SecureRandom Mock: nextBytes byte[] length requested does not match byte[] setup", returnValue.length, output.length);
-
-        System.arraycopy(returnValue, 0, output, 0, returnValue.length);
-
-        return null;
-      }
-    }).when(mock).nextBytes(argument.capture());
-
-    return mock;
-  }
-}

app/src/test/java/org/thoughtcrime/securesms/testutil/SecureRandomTestUtil.kt

@@ -0,0 +1,31 @@
+package org.thoughtcrime.securesms.testutil
+
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.slot
+import org.junit.Assert.assertEquals
+import java.security.SecureRandom
+
+object SecureRandomTestUtil {
+  /**
+   * Creates a [SecureRandom] that returns exactly the {@param returnValue} the first time
+   * its [SecureRandom.nextBytes]} method is called.
+   *
+   * Any attempt to call with the incorrect length, or a second time will fail.
+   */
+  @JvmStatic
+  fun mockRandom(returnValue: ByteArray): SecureRandom {
+    return mockk<SecureRandom> {
+      var count = 0
+      val slot = slot<ByteArray>()
+      every {
+        nextBytes(capture(slot))
+      } answers {
+        assertEquals("SecureRandom Mock: nextBytes only expected to be called once", 1, ++count)
+        val output = slot.captured
+        assertEquals("SecureRandom Mock: nextBytes byte[] length requested does not match byte[] setup", returnValue.size, output.size)
+        System.arraycopy(returnValue, 0, output, 0, returnValue.size)
+      }
+    }
+  }
+}