Alice and Bob are married, engaged, or otherwise attached. Alice gets it into her head to somehow 'test' whether Bob is faithful to her. Sometimes, she believes he is, but makes a wager with someone who insists that he isn't, or that no one else ever is. Alternately, she's just suspicious for no good reason.
Then Alice's agent, or the person with whom Alice made the wager, or Alice herself in disguise, goes and attempts to seduce Bob. In almost all cases, Bob will prove to be true to Alice. Often she doesn't realize it, though; either her agent lies to her, or, in a twist as old as the trope, he sees through her disguise or otherwise becomes privy to her plan, and plays along to teach her a lesson.
- In Urusei Yatsura chapter 25, Lum went to Ataru's classroom disguised as a normal human. She didn't really intend it as a fidelity test (by this point, it's pretty obvious that Ataru would fail), but rather to see whether Mendō's suggestion that Ataru "prefers a girl as ordinary as himself" was true. However, she got upset at Ataru when he told Mendō that "Lum's yours [now]", so she (while in disguise) asked Ataru to promise to be faithful, and when he did, she dropped the disguise and told him "I will hold you to that!"
- There's a commercial (based on a very old joke) where a groom in a tux is propositioned by his fiancee's sister. He runs out the door and gets to the car, when his father-in-law-to-be and a group of other people tell him he passed the test. Then a voice-over "Lesson learned: Always keep Trojans in your car". Here on Youtube.
- Superman manages to do this accidentally to Lois Lane. After Clark and Lois have become a couple, but before he tells her that he's Superman, he forgets himself and asks Lois to dinner while still disguised as Superman, only for her to snap at him, reminding him that she's Clark's girlfriend.
- During the Olympics Plot of Jla Watchtower/DC Nation, Roy Harper challenged the Greek Gods for a chance to resurrect Donna Troy. As part of the test, Aphrodite demanded he remain celibate from the time of the challenge until the actual games. For an Arrow, that was already easier said then done. And then, Aphrodite casts a spell that makes women fall head over heels in lust for him (with only Lian immune), leading to a memorable line out of Ollie...
Green Arrow I: He's not exaggerating, Connor. I watched him do a bad Chippendale's impression, and Dinah was getting excited. Something's off here. Go, teach him how to ignore women's come-ons. * mutters* Lord knows you're the only one here who can manage it.
- In one Sailor Moon fanfic, Serena disguises herself as a hot supermodel and flirts with Darien, assuming he'll fend the false her off while proclaiming his love for the real her. It fails miserably, but only because Darien can tell it's her right away by looking at her eyes.
- In the film Extract, Joel is frustrated that his wife Suzie never wants to have sex, plus he's certain that the new temp is hitting on him. His friend Dean suggests that he set one of these up so that if Suzie is untrue, he can go ahead and have an affair guilt-free. Joel at first refuses, but later gets stoned and hires Brad to seduce his wife as the new pool boy. When he sobers up and realizes what he did, he tries to get in touch with Brad, only to find that he came a day early and already seduced Suzie (and he proceeds to come back numerous times after that, not being quite clear on the concept).
- In the remake of The Thomas Crown Affair (1999), Thomas deliberately makes it appear as though he's having a relationship on the side in order to try to find out if Catherine is just after the painting or not.
- In My Geisha, Shirley Maclaine is an actress who tests her husband's fidelity by disguising herself as a Geisha (using hair dye and contact lenses (hey, it was 1962, and the film audience had rarely seen an actual Japanese actress). She acts in a movie as the Geisha, and her husband only tumbles to her identity when watching the rushes in reverse color. He then shows an interest in her alter ego, who of course gives him the brush-off. At the end he quotes the Geisha's line about about being "sympathy", or genuinely interested in a man. So the wife knows he knows, and there is a happy ending. Query: shouldn't he has be able to see she resembled his wife in other ways?
- The protagonist of This Girls Life starts a fidelity-private eye business. Women hire her to test their mates' commitment, to varying results.
- In Tangled, Mother Gothel proposes that Rapunzel put Flynn to this by giving him the tiara that was the price of guiding her. Rapunzel chickens out, but later does it. Mother Gothel instantly puts her plan into action and makes it convincingly look like he failed it.
- In Rule Of Three (1996), Roger meets and marries Sam, then becomes concerned about her fidelity and asks his best friend Roger to try and seduce her so that her true love can be proven.
- In Kissing a Fool, committment-phobic Chicago sportscaster Max Abbit (David Schwimmer) thinks he's finally found the girl of his dreams in cerebral book editor Samantha (Mili Avital), after Max's best friend, novelist Jay (Jason Lee), fixes them up. But Max, haunted by doubts about his fiancee's fidelity, enlists Jay to test her loyalty by trying to seduce her.
- In The Fidelity Test, Franziska’s job is to act as bait for potentially unfaithful men. Once engaged by a suspicious wife, Franziska presents herself to the husband as an easy conquest until her assistant Alfonso is able to document the infidelity with a camera. So far, she’s never failed…
- In For Love of Evil, when Parry is about to marry the lovely Jolie, a jealous suitor has a unicorn approach, hoping to prove that Jolie is not a virgin. Even her father is totally stunned when the unicorn allows Jolie to stroke it, proving her a virgin.
- A libertine poem by Jean De La Fontaine is about a guy who thinks his wife cheats on her, and so pretends to go on a trip, repeatedly disguising himself as a merchant, a priest and a knight, and seducing her. She gives in every time, and when he confronts her, she says she cheated on him 3 times: with a merchant, a priest and a knight. He realizes she recognized him every time, and thus the Aesop is learned.
- The novel Don Quixote has several smaller novels inside of itself, one of this "The Impertinent Curious", a married man decides to put to test his wife's loyalty through his friend, all goes well until his friend happens to fall in love with his wife and runs off with her after performing a perfectly executed theater making the man believe his wife is faithful. The man eventually commits suicide when he finds out that he was the responsible all along.
- "Cephalus and Procris" in Ovid's Metamorphoses.
- A (possibly) unintentional example in Sergey Lukyanenko's False Mirrors, Leonid's marriage is on the rocks. Meanwhile, he assembles a group of former Divers and hackers and goes into a virtual game to try to find the entrance to the Diver Temple. Along the way, they pick up a female player named Nike. During the journey, Leonid tells Nike he likes her. After the adventure, he takes off his VR helmet to find out that Nike was his wife Vicka in disguise. Realizes he should have guessed Nike's identity, since Nike is the Greek goddess of victory, whose Roman counterpart is Victoria. He fears the consequences of telling Nike he liked her, but his wife is surprisingly understanding, and he realizes that Nike was merely a projection Vicka's self-image, so, really, he was attracted to the same qualities that made him fall in love with Vicka in the first place. Coitus Ensues. It also probably helps that she has a degree in psychology.
- In the BBC sitcom Coupling, there's a business devoted to at least one half of this—setting up fake dates to test the fidelity of committed men. Sally claims that she has no idea of what they were supposed to do if the man stayed faithful.
- The Dick Van Dyke Show has an episode where Rob wants to know how Laura would react to another man's advances. He calls her on the telephone using a fake accent, and is dismayed that she begins to flirt back. It should be noted that Laura knows right away that it's Rob on the phone.
- In Drake & Josh, Josh is convinced that Drake's girlfriend is hitting on him, and sets up one of these with her and with Drake hiding and watching. She really had been hitting on him, but somehow knows Drake is watching and doesn't fall for the ploy.
- In the Silk Stalkings episode "Red Flag", a company sends out attractive women to test the fidelity of men engaged to be married. They're usually hired by the families of the women to make sure the guy won't cheat on her after they're married.
- In an episode of 3rd Rock from the Sun, August put tape over her nose and pretended it had been bitten off in order to test if Tommy would stay with her even without her looks.
- In one episode of Get Smart, Max impersonates his exact double, King Charles to seduce 99. She realizes it's him and plays along, to his horror - until a fake phone call "proves" that the real Max has been at Control headquarters all day, to her horror. Naturally, at some point the real King Charles also turns up, and Hilarity Ensues.
- The reality TV series Cheaters runs on this trope, with men and women who believe their partners are unfaithful setting up scenarios where they can test their partners fidelity.
- One Monk episode began with a woman who was doing this getting discovered, then getting into a fight with the man that ended with her death.
- On The Nanny there is an episode where Fran pretends to be an old friend of Max's who looks exactly like her to see if he is falling for her instead. He sees through it (but only after he notices the price tag hanging out of the back of her dress).
- Most daytime talk shows (like Maury) will use this one on men suspected of cheating. The man will be put in the waiting room with a decoy who pretends to be another guest and comes onto the man, to see how he reacts. 99 times out of 100, the man will go for it, which gives the perfect opportunity for his girlfriend/wife (or the host) to throw it in his face when he says "I would never cheat on you!" The real comedy gold comes when the man attempts to defend himself, though most of the time they simply get mad about being set up.
- Veronica Mars: Veronica is hired by a neurotic girlfriend to test her boyfriend's commitment to her before he can propose, which involves setting up a "temptation scenario" that ends up starring Veronica herself. (We see Veronica has a regular subcontractor for this work, so it presumably comes up more often offscreen.)
- In one episode of Hetty Wainthropp Investigates, while Hetty was busy with a case, Robert and Geoffrey decided to handle another case on their own, in which a man hired them to perform a fidelity test on his girlfriend. However, since Robert was too old and Geoffrey was too young, they hired someone else to do it. She fell for it, and what's more, the man they hired became the mask. The client was angry at Robert and Geoffrey about this, so he refused to pay them.
- In an episode of Bewitched, when Darrin was on a business trip with an attractive secretary, Endora attempted to prove to Samantha that her husband was planning to have an affair by granting him Three Wishes without his knowledge. When circumstances resulted in his return flight being delayed by a freak snowstorm, Samantha reluctantly believed that he wished for the storm and was planning on leaving Darrin when he came back. After learning about Endora's scheme, he used the three wishes to force Endora to fess up and to stop meddling in his and Sam's life for a week, thus proving his fidelity and restoring Sam's trust.
- Queen of the South features a non-romantic example, as Camila arranges to have Teresa captured and threatened by fake federal agents to see if she'll name Camila as her boss. Teresa is smart enough to know that she shouldn't snitch on her boss, and thus passes the test.
- Played with in Supernatural where a Monster of the Week (a ghost) gets picked up from the side of the road by men and attempts to seduce them, killing them if they give in. However she actually won't let them refuse, effectively making her nothing more than a rapist who murders her victim afterwards.
- The Johnny Cash song "Frankie's Man, Johnny" is about a traveling musician named Johnny who has a girlfriend (Frankie) back home. One night during a performance he notices a very attractive redhead in the crowd and attempts to pick up on her after the show (while thinking that what Frankie doesn't know won't hurt her). His plan backfires, however, when the redhead slaps him and reveals that she is Frankie's sister. The experience scares Johnny straight and he never attempts to cheat on Frankie again.
- Kate Bush's "Babooshka":
She wanted to test her husband.She knew exactly what to do:A pseudonym to fool him.She couldn't have made a worse move.
- The "Broken Token" ballads do this—their general pattern is "guy goes away for seven years and his wife/girlfriend promises to be faithful; she is propositioned by a stranger; she refuses; stranger reveals himself to be the original guy and as proof presents the other half of the ring/coin/necklace that she's been carrying around since he left".
- Female example: the song "Sovay", which provides the page quote, in which a woman tests her lover by dressing as a highwayman and attempting to rob him of the ring she gave him, only revealing her identity when he refuses under threat of death. In the last lines she admits she'd have shot the man if he gave up the ring.
- Older Than Feudalism: In the Biblical Book of Numbers 5:11-31, there is a test for a woman suspected of infidelity, to prevent her jealous husband from going on a Roaring Rampage of Revenge without proof and/or from having her executed when it wasn't adultery but a big misunderstanding. The woman was taken to the Temple, and her head covering was removed while some grain was offered at the altar. Meanwhile, the priest wrote a curse on a piece of paper, and sprinkled dust from the floor into a container of water. If the woman was faithful, not only would the cursed water would have no effect on her, but her husband would be obligated to impregnate her. If, however, she was cheating, she would become infertile/barren; it should be noted that among Israelite women barreness was extremely shameful even without the stigma of adultery attached to it.
- In the Ramayana, Sita has been kidnapped and held hostage by Ravana, though she refused his sexual advances. Rama has her walk over fire to purify her...and rather than burning her, the fire does not so much as singe her, proving that she was, in fact, faithful to him. (Some versions have the flames turning into flowers as she walks over them.)
- From Greek Mythology, the tragedy of Cephalus and his wife Procris has one of these. Cephalus was abducted by the goddess of dawn Eos during one of his hunting trips. Cephalus initially doesn't resist, since in Greek Myth it's usually impossible for men to resist goddesses, but he eventually starts pining for his wife. A disgruntled Eos returns him but spitefully insinuates that Procris had also taken other lovers in his absence. Cephalus decides to test his wife by disguising himself and offers Procris more and more money if she would sleep with him. The moment he sees her hesitate he reveals himself and calls her unfaithful. An ashamed Procris flees to become a follower of the hunt goddess Artemis, who calls out Cephalus for being a jerk. Husband and wife eventually reconcile and Procris even brings a couple of souvenirs like a magical spear that always hits its target. The spear is one of the reasons this story ends tragically.
- An Indonesian folk lore of Banyuwangi (literally means Sweet-smelling Water) River. Ida Ayu Surati was a princess escaped from destroyed kingdom, but was saved by and then married the prince who raided her kingdom, Raden Banterang. One day, Ida Ayu Surati met a beggar, who then she recognized as her brother Agung Bagus Mantra. Agung asked his sister to kill her husband for destroying their kingdom, but Ida who grew to love him, refused. Agung then spread a lie about Ida's infidelity, and Banterang who heard it became angry. When confronted by her husband, Ida prophesied that her innocence would be proved by the river's water condition. Already in his wit's end, Banterang stabbed Ida and threw her corpse into the dirty river, which then turned fragrant and clean. One of the examples where the innocent wife dies in the test.
- Several italian folk tales have a version of this, often with the heroine as the testee. In one such case, a woman was imprisoned by her lover's ogress mother, who insisted she complete impossible tasks under pain of death (the mother wanted the excuse to kill her so she could marry her son to a princess.) The woman would attempt the task, realize she was going to fail, and have a handsome youth appear to her and offer to complete the task in exchange for a kiss. The woman refuses each time—if he were her lover, a thousand kisses, but he is not and will not get one— and the youth completes the tasks for her anyway, finally revealing that he is her lover after the last task. He gets the thousand kisses.
- In Cymbeline by William Shakespeare, Posthumus makes a wager with Iachimo that his wife Imogen will be true to him. Iachimo fails to seduce her, but claims otherwise.
- There's a Chinese opera whose plot runs thus: a poor man lands the luck of marrying a wealthy lady, and to raise his station in life he goes off to study for the Imperial Exams. Years later, he returns with a government post, and decides to test her faithfulness. Not only does she prove to be the iron lady, she gets quite pissed when he reveals himself and he has to beg for her forgiveness. (If I recall correctly, she lets him sweat for a while before doing so.)
- In Così Fan Tutte, Ferrando and Guglielmo make a bet with Don Alfonso and he concocts the Zany Scheme in which they attempt to seduce their girlfriends disguised as Albanians.
- In The Merchant of Venice, Portia and her servant test the fidelity of their newly-acquired husbands by demanding their wedding rings after saving the life of their friend, Antonio (it's complicated—there's drag involved). The men do fail the test, and the wives lord it over them for the rest of the play.
- In Die Fledermaus, Gabriel von Eisenstein goes off to a party after telling his wife Rosalinde he's going to be somewhere else. A mutual acquaintance tips off Rosalinde, who goes to the party in disguise to see how he behaves — and he, not recognising her, immediately attempts to seduce her with a trinket he's successfully used in the past on other women. She gets out of the situation with her dignity intact and with the trinket, which she later shows her husband to let him know she knows he's been misbehaving.
- Europe 2, a Czech commercial radio station, used to have a segment called "Fidelity Test" as a part of their morning show in the Naughties. Usually, it never went well for those who ordered it. The radio hosts were asked to call their significant others and try to seduce them, usually just asking for a date. In vast majority of cases, the men (and mostly they were men) agreed to go. If they were in fact committed to the relationship, they got furious for lack of trust or for being suspected or being tested. There were many immediate break-ups. When the show got more known, some call-ees proved genre-savyy and refused to go, but admitted they knew what was happening — and got pissed off anyway.
- Z104.3, a Baltimore music station, has a similar segment with an arguably more effective variation. The station calls the suspected cheater, with the (usually female) accuser listening in, and claims that he's won a romantic gift package- flowers, massage/spa for two, etc. Then they ask who he'd like to send the package to. When the target doesn't pick the woman listening in, and they frequently don't, things tend to get ugly.
The Merchant Of Venice features an ostensibly non-sexual variant. Portia and Nerissa give rings to their respective lovers, Bassanio and Gratiano, extracting a promise that they will never give said rings to anyone else. Then Portia, pulling a Sweet Polly Oliver in the guise of a young lawyer, saves the life of Bassanio’s friend Antonio and demands the rings as payment. The men fail the test, but the women forgive them after revealing the truth, content that they’ve learned their lesson. Whether Bassanio giving up his girlfriend’s ring to a handsome young lawyer is meant to have sexual subtext is open to interpretation, but given the sheer volume of Ho Yay in the play and the fact that giving someone a ring was one of many symbols that the dirty-minded Elizabethans associated with sex…
- Late in the game of Lufia II: Rise of the Sinistrals, the party arrives at a town with a dungeon tower that houses the Mirror of Truth, a famous mirror in the area that couples go to confirm each other's fidelity. The mirror reflects the image of the faithful lover while it fails to reflect the image of a cheater. Iris, secretly a conflicted antagonist of the Big Bad's group, tests/prods the hero Maxim and his wife Selan to venture to the Mirror of Truth after implying that the couple's trust in each other is weak (and the rest of the party accidently alluding the possibility that Maxim might had a fling with Iris didn't help) thus causing the latter to demand to test their faithfulness in the mirror. Ultimately, just prior to entering the mirror room Maxim wins Selan over again saying he would would trust each others' faithfulness even if the mirror indicated otherwise. Soon after they enter the room, a swarm of monsters come to attack the party, pushing them deeper into the room with their backs facing the mirror. The mirror reflects both their backsides as the battle commences, but the mirror is destroyed in the process of the fight so they never actually determine what the mirror says about them.
- Relatively early in General Protection Fault, Ki tries to pull one on Nick. Using an old IRC handle she'd previously used to flirt anonymously with him. It fails, with Nick revealing to the audience that he knew who "Pookle" is.
- In Futurama, Bender becomes convinced that his girlfriend Angeline is cheating on him with Flexo (who is almost identical to Bender, if only it weren't for the beard). Bender disguises himself as Flexo and proceeds to seduce Angeline by acting exactly like Bender (or at least not like Flexo). After resisting for a long time, she gives in (as Flexo appears to be nothing like she'd thought): Bender triumphantly reveals himself, taking this as proof that she was cheating on him:
Bender: AHA! You love Flexo so much, you even love anyone pretending to be him!
Angeline: Maybe I love you so much, I'd fall for you no matter who you're pretending to be!
Bender: Oh, if only I could believe or even understand that!
- In the 80s show Jem and the Holograms, Jerrica is constantly worried about the fact that her boyfriend Rio is two-timing her with her holographic persona Jem. In one episode, she decides to test him by creating a third (holographic) persona - whom he instantly falls in love with. This proves to her that it's really her that he's loved the whole time.
- One episode of Archer sees the men of the Figgis Agency hired to seduce the wife of a producer, not realizing that the women of the agency have been hired by the wife to seduce the producer.
- In the American Dad! episode "Choosy Wives Choose Smith", Francine's hunky ex-boyfriend visits Langley Falls and Stan, feeling inadequate, is convinced by Roger to test whether she still carried a torch for him. So he and Roger fly out to a CIA vacation spot in the Pacific, making it look like they were lost at sea...only for them to get stranded for real when a tsunami strikes the island. When they finally make it home, Francine reveals that she knew it was a test all along (thanks to Stan's Incredibly Obvious Bug) and was stringing her ex along just to mess with Stannote . The ex angrily storms off after declaring that Stan and Francine are perfect for each other because they're both assholes.
- There are quite a few agencies that aim at seducing one's husband, in order to prove that he's unfaithful. Or capable of being so. What's funny about that actually using this trope in real life implies that half of the relationship has no trust in the other. Which means its already in trouble regardless of the result. Which only proves true the quote, "Marriages don't fall apart because of infidelity. Infidelity is just a symptom of a larger problem."
- A girl hires a pornstar to test her boyfriend. The pornstar approaches the guy in public and openly hits on him. He's a little put off by her and wonders what she wants with him. At the end, though, he does accept her phone number. The girlfriend is a little upset at this and calls him afterwards to confront him. The result? He dumps her over the phone for this lack of trust, and she feels that he had no right to do that.
- The legal principle of Condonation can give rise to a strange inversion of this trope by allowing someone to prove that their partner knowingly accepted their infidelity. One lawyer describes someone who was caught having an affair, then tried to pull a Honey Trap on their spouse, since continuing to have sex would be evidence that the spouse condoned their affair.
- There's an old joke-cum-urban-legend that subverts this trope. A wife who disguises herself and follows her husband to a costume party. She seduces him as a Fidelity Test, but learns later that he gave his costume to someone else.
- A joke goes that a man woke up one morning with a bad hangover. He discovered his robe had just been washed and ironed, and when he came downstairs, he found his wife had also washed his suit, put on a fresh pot of coffee, and was cooking a big breakfast. When he asked what was with the special treatment, the wife explained that he'd come home drunk at 3:00 am and passed out on the lawn, then soiled himself. To avoid the neighbours seeing, she dragged him inside and tried to get him out of his dirty clothes, but when she pulled off his trousers, he exclaimed "Piss off lady, I'm married!"
- Another old joke: a man and his fiancee have dinner at his future in-laws' house the week before their wedding. Complaining of a headache, the fiancee leaves early to lie down. Her parents also turn in early, leaving the man alone with his fiancee's beautiful younger sister. The younger sister confesses that she's always had a crush on the man, and tells him that if he's interested in a wild night of no-strings-attached sex before he becomes a married man, to follow her up to her bedroom, and if not, to go home and she'll never bring it up again. The man walks out the front door to find his fiancee and her parents waiting for him; his fiancee and future mother-in-law hug him and his future father-in-law shakes his hand and says, "You passed the test. Welcome to the family, son." The moral of the story? Always leave your condoms in the glove box.