Add unit test for no active book issue

Author: rivaldi8

app/src/test/java/org/gnucash/android/test/unit/db/BooksDbAdapterTest.java

@@ -36,6 +36,7 @@
 
 import javax.xml.parsers.ParserConfigurationException;
 
+import static junit.framework.Assert.fail;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -158,6 +159,26 @@ public void testGeneratedDisplayNames_shouldBeUnique(){
         assertThat(generatedName).isEqualTo("Book 4");
     }
 
+    @Test
+    public void recoverFromNoActiveBookFound() {
+        Book book1 = new Book(BaseModel.generateUID());
+        book1.setActive(false);
+        mBooksDbAdapter.addRecord(book1);
+
+        Book book2 = new Book(BaseModel.generateUID());
+        book2.setActive(false);
+        mBooksDbAdapter.addRecord(book2);
+
+        try {
+            mBooksDbAdapter.getActiveBookUID();
+            fail("There shouldn't be any active book.");
+        } catch (BooksDbAdapter.NoActiveBookFoundException e) {
+            mBooksDbAdapter.fixBooksDatabase();
+        }
+
+        assertThat(mBooksDbAdapter.getActiveBookUID()).isEqualTo(book1.getUID());
+    }
+
     /**
      * Creates a new database with default accounts
      * @return The book UID for the new database