The Supreme Court has yet to decide whether a citizenship question will be included in the 2020 census, but the Census Bureau is launching a test Thursday to observe how the addition of such a question might impact response rate.

The test is aiming at determining “the operational effects of including a citizenship question on the 2020 Census,” according to the Bureau press release.

Some 480,000 housing units around the nation will receive a questionnaire with households randomly assigned to one of two versions of the questionnaire: one with the citizenship question included, the other without. The test is also designed to oversample housing units in areas with “high proportions of non-citizens and historically low self-response.”

Terri Ann Lowenthal, a former staff director of the House Oversight subcommittee for the census and consultant, said conducting a test of this magnitude so close to the start of the 2020 census is “unprecedented” and has “potential for confusion” with the actual census.

“They might think to themselves, ‘I already got that, and I already filled it out,’” Lowenthal said.

The final preparations for the 2020 census should be on autopilot, but Commerce Secretary Wilbur Ross’ late notice of the decision to add the citizenship question and the much-awaited Supreme Court decision has left the Census Bureau in a difficult position to prepare.

“The eleventh-hour decision by Secretary Ross was comparable to throwing a hand grenade in the middle of a carefully planned multi-year effort to pull off the census,” Lowenthal said. “The Census Bureau was left with no time to prepare, plan, and conduct another large test.”

“The Census Bureau does multi-year iterative testing,” Lowenthal told ABC News. “That’s why a decision to add a new question that has not been part of any testing for this census, I think, you know, was highly irresponsible. It went against all traditional procedures, and you know scientific standards for making that kind of decision,” she added.

By launching this test, the Bureau is trying to prepare for the potential outcome of having the citizenship question as part of the 2020 census.

Data collection will run from June 13th to August 15th, 2019, and the preliminary results for the test will be released in October 2019. The findings from the test will help inform updates to the Bureau’s 2020 operations including the number of census takers needed to follow up with non-responding households.

Lowenthal said it would be wise to hold off on the test until the Supreme Court ruling, but that the Census Bureau feels it must move forward with the test because time is of the essence.

“I think the Census Bureau should cancel the test if the Supreme Court upholds the lower court ruling prohibiting the Commerce Secretary from adding this question,” she told ABC News. “But the Census Bureau believes it has to move forward at this point of time. That it doesn’t have give in its schedule in preparing to start the census."

The Trump administration has pushed for the citizenship question deeming the number and locations of non-citizens as necessary information for the Justice Department to enforce the Voting Rights Act. Critics have stated that including such a question could deter non-citizens — both legal and illegal residents — from responding and undercount a significant portion of Latinos and immigrants. This could skew the population totals used to draw legislative districts and potentially provide Republicans with an electoral advantage.

According to a study by the Harvard Shorenstein Center on Media, Politics and Public Policy, the citizenship question would lead to an undercount of 6 million Hispanics, approximately 12% of the total Hispanic population. The Census Bureau told the White House in February that they expect 630,000 households to either submit the survey without the citizenship question answered or to not reply at all.

The Supreme Court is expected to come to a decision by the end of the month on whether the addition of a citizenship question is constitutional.