AngularJS ngClass conditional

Your first attempt was almost right, It should work without the quotes.

{test: obj.value1 == 'someothervalue'}

Here is a plnkr.

The ngClass directive will work with any expression that evaluates truthy or falsey, a bit similar to Javascript expressions but with some differences, you can read about here. If your conditional is too complex, then you can use a function that returns truthy or falsey, as you did in your third attempt.

Just to complement: You can also use logical operators to form logical expressions like

ng-class="{'test': obj.value1 == 'someothervalue' || obj.value2 == 'somethingelse'}"

Using ng-class inside ng-repeat

<table>
    <tbody>
            <tr ng-repeat="task in todos"
                ng-class="{'warning': task.status == 'Hold' , 'success': task.status == 'Completed',
              'active': task.status == 'Started', 'danger': task.status == 'Pending' } ">
                <td>{{$index + 1}}</td>
                <td>{{task.name}}</td>
                <td>{{task.date|date:'yyyy-MM-dd'}}</td>
                <td>{{task.status}}</td>
            </tr>
    </tbody>
</table>

For each status in task.status a different class is used for the row.