Aung San Suu Kyi has been in detention without trial for more than 13 of the past 19 years.
Not guilty plea
Her testimony comes after she pleaded not guilty to the charges against her in front of the prison tribunal on Friday.
But the court said it accepted the case against her and the trial will proceed to a verdict.
The court also accepted the charge levelled against two of Aung San Suu Kyi's companions and John Yettaw, an American man whose intrusion into her lakeside home triggered the case.
Yettaw, a Vietnam War veteran from the US state of Missouri, is alleged to have visited her home twice, swimming across Yangon's Inya lake to avoid security.
He was arrested in early May as he attempted to swim back from the second visit.
Prosecutors say Aung San Suu Kyi violated the terms of her house arrest by giving Yettaw shelter, but her lawyers say she only allowed him to stay after he pleaded with her that he was too unwell to move.
On Monday prosecutors abruptly dropped the nine remaining witnesses they had planned to call, fuelling speculation that the trial could end in days.
"If the hearing continues like this, the entire process will come to an end in three or four days," Nyan Win, one of four lawyers representing Aung San Suu Kyi, told reporters.
|Aung San Suu Kyi briefly met with foreign diplomats last week [AFP]
Myanmar's government has said it will allow a group of foreign diplomats and media into the court on Tuesday to hear her testimony.
"We have been told to gather at the prison at 7.30am," an Asian diplomat told Reuters news agency.
Diplomats who were given a brief glimpse of the trial last week said it appeared "scripted", but the government insists the trial "will proceed fairly according to the law".
"It could be they have already written the verdict," said Nyan Win, who complained the defence team was not able to meet privately with Aung San Suu Kyi before she testifies.
Opposition supporters and Western governments critical of Myanmar have condemned the trial, labelling it a pretext for the government to keep Aung San Suu Kyi in detention beyond national elections it has scheduled for next year.
The government says the vote will mark the culmination of Myanmar's "roadmap to democracy," but critics say the regulations surrounding the election mean it will only cement continued military control.
Myanmar has been under military rule since 1962.
It last held an election in 1990, but the government refused to recognise the results after a landslide victory by the NLD.