Add documentation for CollectionUtils#arrayAsList

(This is a cherrypick of http://ag/576739)

Also, modify the IllegalArgumentException to capture the
values passed for start, end, and array.length to make
debugging easier in the unlikely event that it is thrown.
Add corresponding tests for the exceptions.

Tested:
tapas LatinImeGoogle LatinImeGoogleTests userdebug
make -j30 && \
adb install -r \
out/target/product/generic/data/app/LatinImeGoogleTests/LatinImeGoogleTests.apk && \
adb install -r \
out/target/product/generic/system/app/LatinImeGoogle/LatinImeGoogle.apk && \
adb shell am instrument -w -e class \
com.android.inputmethod.latin.utils.CollectionUtilsTests \
com.google.android.inputmethod.latin.tests/android.support.test.runner.AndroidJUnitRunner

Change-Id: I0c579ca4f4f2a9b2575aa6f8fa75e3ee4a21cf8a

1 files changed, 32 insertions, 1 deletions

diff --git a/tests/src/com/android/inputmethod/latin/utils/CollectionUtilsTests.java b/tests/src/com/android/inputmethod/latin/utils/CollectionUtilsTests.java
index a5979c3df..dc4e2e4bb 100644
--- a/tests/src/com/android/inputmethod/latin/utils/CollectionUtilsTests.java
+++ b/tests/src/com/android/inputmethod/latin/utils/CollectionUtilsTests.java
@@ -29,14 +29,45 @@ import java.util.Collections;
 @SmallTest
 public class CollectionUtilsTests extends AndroidTestCase {
     /**
+     * Tests that {@link CollectionUtils#arrayAsList(Object[],int,int)} fails as expected
+     * with some invalid inputs.
+     */
+    public void testArrayAsListFailure() {
+        final String[] array = { "0", "1" };
+        // Negative start
+        try {
+            CollectionUtils.arrayAsList(array, -1, 1);
+            fail("Failed to catch start < 0");
+        } catch (final IllegalArgumentException e) {
+            assertEquals("Invalid start: -1 end: 1 with array.length: 2", e.getMessage());
+        }
+        // start > end
+        try {
+            CollectionUtils.arrayAsList(array, 1, -1);
+            fail("Failed to catch start > end");
+        } catch (final IllegalArgumentException e) {
+            assertEquals("Invalid start: 1 end: -1 with array.length: 2", e.getMessage());
+        }
+        // end > array.length
+        try {
+            CollectionUtils.arrayAsList(array, 1, 3);
+            fail("Failed to catch end > array.length");
+        } catch (final IllegalArgumentException e) {
+            assertEquals("Invalid start: 1 end: 3 with array.length: 2", e.getMessage());
+        }
+    }
+
+    /**
      * Tests that {@link CollectionUtils#arrayAsList(Object[],int,int)} gives the expected
      * results for a few valid inputs.
      */
     public void testArrayAsList() {
-        final String[] array = { "0", "1", "2", "3", "4" };
         final ArrayList<String> empty = new ArrayList<>();
+        assertEquals(empty, CollectionUtils.arrayAsList(new String[] { }, 0, 0));
+        final String[] array = { "0", "1", "2", "3", "4" };
         assertEquals(empty, CollectionUtils.arrayAsList(array, 0, 0));
         assertEquals(empty, CollectionUtils.arrayAsList(array, 1, 1));
+        assertEquals(empty, CollectionUtils.arrayAsList(array, array.length, array.length));
         final ArrayList<String> expected123 = new ArrayList<>(Arrays.asList("1", "2", "3"));
         assertEquals(expected123, CollectionUtils.arrayAsList(array, 1, 4));
     }