@Test
public void mergeSingleThemeNoLayers() {

    final Theme theme = createTheme( "Theme", -180.0, -90.0, 180.0, 90, null, null, null );
    final LayerMetadata merged = merger.merge( theme );
    assertEquals( "Theme", merged.getName() );
    final Description description = merged.getDescription();
    assertSingleEntry( "Theme Title", description.getTitles() );
    assertSingleEntry( "Theme Abstract", description.getAbstracts() );
    final SpatialMetadata spatialMetadata = merged.getSpatialMetadata();
    assertEquals( "EPSG:4326", spatialMetadata.getCoordinateSystems().get( 0 ).getAlias() );
    assertEquals( -180.0, spatialMetadata.getEnvelope().getMin().get0(), 0.0000001 );
    assertEquals( -90.0, spatialMetadata.getEnvelope().getMin().get1(), 0.0000001 );
    assertEquals( 180.0, spatialMetadata.getEnvelope().getMax().get0(), 0.0000001 );
    assertEquals( 90.0, spatialMetadata.getEnvelope().getMax().get1(), 0.0000001 );
}