When it comes to the Bechdel Test, a lot of people miss what I see as its biggest strength.
The Bechdel Test is not about the stereotype that women always talk about men. I've seen folks, both pro-woman and not, bend the test into a pretzel to show how the story they're testing does or does not support that stereotype.
On the side of folks who want to see more well-rounded women in popular media, that looks like what gamers call hardcore rules lawyering: construing "two women must talk to each other about something other than a man" to mean "two named women must talk to each other and must not discuss men at all," or at least "must have at least one conversation in which men are not discussed, no matter how many other topics are covered." This raises a lot of questions, which then require corallaries: What counts as 'named?' Do they have to be called by name on screen, or is it sufficient for the character to be named in the credits? What counts as the start and end of a conversation, for the purposes of excluding conversations where men are discussed? Etc etc etc.
On the other side, apologists for media that doesn't pass will insist that stories can have strong women characters without passing. One author who was called out for failing the test suggested that any test that would criticize a police procedural about women taking down a male crime boss while praising a comedy where two women discuss shoes is not a test he wants to concern himself with passing. That author was missing the point by as wide a margin as the rules-lawyers.
Stories aren't like real life. They're groups of interwoven narratives. They glaze over the unimportant bits so they can focus on the parts that further the plot and the characterization of the most significant people. This is especially true for movies--which, let's not forget, is the medium for which the Bechdel test was created. Movies have to cover a lot of ground in a very short span of time, so they have to be ruthless about leaving out things that don't serve the narrative.
In that context, the Bechdel Test's real strength is its ability to measure how important women are to the narratives of a given story.
A story in which two women are talking to each other about shoes is a story about those women, their relationship to each other, and their relationship to shoes. That might seem like a boring story to you, but it's their story.
By contrast, if a story about two women taking down a male crime boss fails the test because they only ever discuss the crime boss, then the story is not about them. It's about the crime boss.
Whether a story can have a strong woman in it without passing the Bechdel test is not the point. The point is that if a story fails, that's a pretty good indication that the women in it--however strong, brave, smart, worthy, etc--are not there to tell their own stories. They're there to help tell a story about men.
And let's be realistic: we've seen stories about women detectives. Cagney and Lacey. Rizzoli & Isles. Bones. They don't have any trouble passing the Bechdel test, because the characters don't just talk about the criminals they're taking down. They talk about ordering takeout, how their work is affecting them, who's car to take to a crime scene, what they did over the weekend, how they like their coffee, and--yes--shoes. When the story is actually about the women, those conversations get included, because the narrative they support--the narrative about the women themselves, their relationships to each other, their inner lives outside of crime-boss hunting--are deemed important to the story.
Which is why the test works for other marginalized groups as well: conversations between people of color about something other than a white person indicate that at least one of the story's narratives is about people of color (and their lives outside of their relationship to white folks). The same can be said about conversations between disabled characters, LBGT characters, and characters who are marginalized in other ways.
The point isn't the stereotype that women always talk about men. The point is that stereotype exists in the first place because our culture is more interested in men's narratives than ours. The overwhelming majority of films leave our narratives out. Passing the Bechdel test means that at least in some small way, the passing work is telling a story about women, rather than just with them.