Devendra Fadnavis resigned as the chief minister on Tuesday after NCP's Ajit Pawar broke the alliance.
The floor test is a constitutional mechanism under which a chief minister can be asked to prove majority in the state Assembly.
Ajit Pawar had last week rebelled against his party and pledged NCP's support to BJP to form government in the state.
Ajit Pawar gave the letter of support of 54 NCP MLAs to Governor as the leader of his legislature party which resulted in a BJP-NCP government formation in the state on Saturday.
The BJP was propped up by NCP's Ajit Pawar who revolted against his party headed by his uncle Sharad Pawar.
Gehlot claims the sordid drama in Maharashtra on Saturday was possible only with the blessings of Modi
The Nationalist Congress Party had on Saturday moved 44 MLAs to Renaissance Hotel in Mumbai.
The top court while hearing the NCP-Sena-Congress plea against BJP-lead government formation in the state said appropriate orders will be passed on Monday.
NCP President Sharad Pawar met his party legislators at Hotel Renaissance along with Nawab Malik, and were later joined by Shiv Sena senior leaders.
Earlier, the plan of action was to take them to Gujarat but sources say they may now be moved to the state later.
Thackeray said this was nothing but a sheer mockery of democracy - first in Bihar, then in Haryana and now in Maharashtra, and whatever has happened is not according to the Constitution.
A Congress leader said except for two of its MLAs who had gone to their village, all their MLAs are in Mumbai.
Ajit Pawar, the nephew of NCP supremo Sharad Pawar, took oath at Raj Bhavan along with BJP's Fadnavis, who became the CM of the state for a second consecutive term.
The Congress leader said that none of the NCP MLAs will support Ajit Pawar. Singh also asked the Shiv Sena to hit the streets to show their power in Mumbai.
Hard at work was the BJP national general secretary Bhupendra Yadav, who had been tasked by the top brass with completing the formalities of ushering in a government led by Devendra Fadnavis.