For those interested you can look up citizenship Mandamus cases on Canlii. Here are some cases I found from the last 3 years and a brief summary of the reasons why the mandamus application was dismissed or accepted:
1.
https://www.canlii.org/en/ca/fct/doc/2020/2020fc1029/2020fc1029.html?searchUrlHash=AAAAAQAIbWFuZGFtdXMAAAAAAQ&resultIndex=1 (Mandamus denied, IRCC officer had suspended the citizenship application because of info received from Interpol regarding outstanding criminal charges against the applicant).
2.
https://www.canlii.org/en/ca/fct/doc/2019/2019fc590/2019fc590.html?searchUrlHash=AAAAAQAIbWFuZGFtdXMAAAAAAQ&resultIndex=4 (Mandamus denied, IRCC officer suspended citizenship application while investigating applicant's father's citizenship - applicant had applied as a child of a Canadian citizen. IRCC received info leading them to initiate citizenship revocation proceedings against the father, who had failed to disclose all his absences from Canada prior to citizenship application).
3.
https://www.canlii.org/en/ca/fct/doc/2019/2019fc938/2019fc938.html?searchUrlHash=AAAAAQAIbWFuZGFtdXMAAAAAAQ&resultIndex=6 (Mandamus denied, multiple lies, misrepresentations and fraud committed by the applicant, name change, failing to respond to two requests for fingerprints, IRCC becoming aware of multiple murder attempt charges against applicant in his country of origin).
4.
https://www.canlii.org/en/ca/fct/doc/2019/2019fc756/2019fc756.html?searchUrlHash=AAAAAQAIbWFuZGFtdXMAAAAAAQ&resultIndex=10 (Mandamus denied, IRCC suspended the citizenship application pending the determination of refugee status cessation proceedings - applicant claimed refugee status but made multiple trips to his country of origin)
5.
https://www.canlii.org/en/ca/fct/doc/2020/2020fc452/2020fc452.html?searchUrlHash=AAAAAQAIbWFuZGFtdXMAAAAAAQ&resultIndex=13 (Mandamus application was considered moot as IRCC lifted the suspension and resumed processing of the case following the initial mandamus court hearing. The Judge did not order any set time for IRCC to complete the processing, instead required the parties to report to the Court on a monthly basis as to the status of the application, so that any outstanding issues or further delays could be addressed promptly).
The judges' decisions, reasoning, determination of whether the Mandamus test is met and their reasons for granting or denying it makes for interesting reading. I encourage everyone considering Mandamus to read some of these cases just to gain some insight into how the judge evaluates each case.