Mosimane's side will face Egypt in an international friendly at Cairo International Stadium on Sunday, following a perfect start to their AFCON qualifying campaign against Guinea and Eritrea.
Johnson believes Bafana should welcome the opportunity to test themselves against the continent's best.
Ex-Bafana coach Hugo Broos previously questioned the value of playing high-profile opponents after his side suffered a 5-0 defeat to France, arguing that such matches could have a negative impact on a young squad.
Broos also turned down an opportunity to face Morocco when Mamelodi Sundowns players were unavailable because of their CAF commitments.
Johnson, who previously worked alongside Mosimane at Al Ahly, believes the Egypt match provides the current Bafana coach with an important opportunity to look beyond his established starting XI.
"You won both AFCON matches, and you won the last one by a significant margin. Against Egypt on Sunday, you should test the players who have not yet been tested so that you can make positive assessments ahead of your next match," Johnson tells KickOff.
With AFCON scheduled for next year, Johnson feels Bafana cannot afford to avoid difficult assignments if they want to be properly prepared for the tournament.
"It is fair for Pitso to play against teams such as Egypt because AFCON is coming up next year. You need to play the strongest countries to prepare properly."
However, Johnson also highlighted the importance of ensuring that international friendlies meet FIFA's requirements if teams want the results to count towards their rankings.
"Several other factors affect rankings in friendly matches. I remember that we made a mistake once when we played Spain a long time ago. We beat them 1-0, but because Spain made eight substitutions, the match was not considered one that would affect the rankings. You must therefore comply with FIFA's rules for a friendly to affect the rankings," he added.
Nigeria coach Eric Chelle reportedly considered calling up Tochukwu Nnadi for the Super Eagles' recent international fixtures, but the midfielder opted to remain in France to continue his recovery from injury.
Bafana Bafana defender Olwethu Makhanya has continued his impressive rise in Scottish football after being named the Scottish Premiership Player of the Month for September after commanding performances for Rangers.
CAF president Patrice Motsepe has revealed that the organisation is discussing keeping the Africa Cup of Nations (AFCON) on a two-year cycle instead of moving to a four-year format.
Kaizer Chiefs have confirmed that they are closely monitoring forward Luke Baartman after he picked up an injury while on international duty with the South African Under-23 team.
