For details on how and where errors are displayed, go here.
Run All Unit Tests optionPython: Run All Unit Test from the command palette

Run Failed Unit Tests optionPython: Run Failed Unit Test from the command palette
Select the file in the explorer and select the Run Unit Tests context menu option

Test code lens display just above the test class (test suite)
Option 1:
Run Unit Test Method ... option
Python: Run Unit Test Method ... from the command palettereturn/enter key
Option 2:
Test code lens display just above the test function/method
Python Test Log output panelQuick Pick List
For details on how and where errors are displayed, go here.
Run All Unit Tests optionPython: Run All Unit Test from the command palette

Run Failed Unit Tests optionPython: Run Failed Unit Test from the command palette
Select the file in the explorer and select the Run Unit Tests context menu option

Test code lens display just above the test class (test suite)
Option 1:
Run Unit Test Method ... option
Python: Run Unit Test Method ... from the command palettereturn/enter key
Option 2:
Test code lens display just above the test function/method
Python Test Log output panelQuick Pick List