Ensure the balancing split has positive amount and the proper transaction type

Splits should always have positive amounts. Whether their amounts are added or
substract is controled by the type of transaction: debit or credit.

The problem was some unbalanced transactions were getting an
auto-balance split with negative amount. When exported to QIF
QifExporter might add a minus according to the transaction type, so
ending up with a double minus.

Fixes #693

Author: rivaldi8

app/src/main/java/org/gnucash/android/model/Transaction.java

@@ -178,7 +178,8 @@ public Split createAutoBalanceSplit(){
         if (!imbalance.isAmountZero()){
             // yes, this is on purpose the account UID is set to the currency.
             // This should be overridden before saving to db
-            Split split = new Split(imbalance.negate(), mCommodity.getCurrencyCode());
+            Split split = new Split(imbalance.abs(), mCommodity.getCurrencyCode());
+            split.setType(imbalance.isNegative() ? TransactionType.CREDIT : TransactionType.DEBIT);
             addSplit(split);
             return split;
         }

app/src/test/java/org/gnucash/android/test/unit/model/TransactionTest.java

@@ -5,10 +5,10 @@
 import org.gnucash.android.model.Money;
 import org.gnucash.android.model.Split;
 import org.gnucash.android.model.Transaction;
+import org.gnucash.android.model.TransactionType;
 import org.gnucash.android.test.unit.testutil.GnucashTestRunner;
 import org.gnucash.android.test.unit.testutil.ShadowCrashlytics;
 import org.gnucash.android.test.unit.testutil.ShadowUserVoice;
-import org.gnucash.android.ui.transaction.SplitEditorFragment;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.robolectric.annotation.Config;
@@ -76,4 +76,32 @@ public void settingUID_shouldSetTransactionUidOfSplits(){
 				.doesNotContain("non-existent")
 				.doesNotContain("pre-existent");
 	}
+
+	@Test
+	public void testCreateAutoBalanceSplit() {
+		Transaction transactionCredit = new Transaction("Transaction with more credit");
+		Split creditSplit = new Split(new Money("1", "EUR"), "test-account");
+		creditSplit.setType(TransactionType.CREDIT);
+		transactionCredit.addSplit(creditSplit);
+		Split debitBalanceSplit = transactionCredit.createAutoBalanceSplit();
+
+		assertThat(creditSplit.getValue().isNegative()).isFalse();
+		assertThat(debitBalanceSplit.getValue()).isEqualTo(creditSplit.getValue());
+
+		assertThat(creditSplit.getQuantity().isNegative()).isFalse();
+		assertThat(debitBalanceSplit.getQuantity()).isEqualTo(creditSplit.getQuantity());
+
+
+		Transaction transactionDebit = new Transaction("Transaction with more debit");
+		Split debitSplit = new Split(new Money("1", "EUR"), "test-account");
+		debitSplit.setType(TransactionType.DEBIT);
+		transactionDebit.addSplit(debitSplit);
+		Split creditBalanceSplit = transactionDebit.createAutoBalanceSplit();
+
+		assertThat(debitSplit.getValue().isNegative()).isFalse();
+		assertThat(creditBalanceSplit.getValue()).isEqualTo(debitSplit.getValue());
+
+		assertThat(debitSplit.getQuantity().isNegative()).isFalse();
+		assertThat(creditBalanceSplit.getQuantity()).isEqualTo(debitSplit.getQuantity());
+	}
 }