Although this question is more fit for ELL but I'll try to explain.
Active
Active voice describes a sentence where the subject performs the action stated by the verb.
For example:
John washed the dishes two hours ago.
Let's break it down:
- Subject: John
- Verb: washed (past)
- Object: the dishes
Therefore in active voice, you always have a subject (John) that is performing an action (Washing the dishes).
Passive
In passive voice sentences, the subject is acted upon by the verb.
Same example in passive voice:
The dishes were washed two hours ago.
Again breaking it down:
- Subject: The dishes
- Verb: were washed (passive past)
So as you see, in the passive voice, washing (verb) is acted upon the dishes (subject). By who? We don't know/care.
Active vs Passive voice? (When do we use them)
Usually, when the action itself is more important than the doer of the action, you use passive form.
Another situation would be, if you don't know who did an action or you don't care who did it, then you use passive.
So for example, When I say "The dishes were washed two hours ago.", I'm not saying who did it. Maybe because I actually don't know who did that, or maybe I don't care. Or maybe it's because it's not important who did it, the important thing is that they are washed.
In other situations, Active is usually preferred.
As stated by @Lynn in this answer, please keep in mind that:
In many styles of writing, active voice is preferred over passive voice for clarity and easier reading. However, in other styles of writing (particularly technical/legalese, which it sounds like you're quoting from), the more stilted sound of passive voice is more common - and perhaps even preferred.
Original Example:
You're (corrected) original line was:
If i run a test on my PC (I am a software tester) and it gets failed fails
Then you asked if you should say
"My test is failing" is a correct active sentence although its tense is not quite right. To fix the tense, you should instead say: "My test has failed." or "My test failed". (because it happened in the past)
For instance:
My test has failed because of a programming bug.
It's still active because as mentioned before, you have a subject (My test) that is doing something (failing).
This is not a correct passive voice. If you want to say it passively, you should instead say: "My test is failed". But it still sounds unusual. In this particular example, I'd use the active voice for clarity. You could definitely say something (passive) like:
If my test is failed, then...
But the active form is more clear and is preferred
If my test fails, then...
Conclusion
Use active for this particular example but as the rule of thumb, if you don't know when to use Active and when to use Passive, ask yourself which one is more significant. If the doer of the action is more important use active or if the action itself is more important, use passive.
Best Answer
This is a special use of the verb to suppose that only occurs in passive contexts (where the actual "agent" doing the "supposing" is unspecified). But hopefully you can see how the more common meaning to suppose = assume / think / guess stretches through to expect to anticipate / plan for / intend [that something will happen, or be true].
Note that...
...doesn't really make sense at the semantic level, but if we change become to plain be it would mean that (unspecified) people believed / were under the impression that Harry actually was an earl. Note that exactly the same substitution wouldn't make any difference to the meaning of the supposed version as given above.
EDIT: I just realized there are perfectly ordinary contexts where the superficially "unusual" syntactic structure in #2 above is unexceptional. For example...
So perhaps Harry was a fervent socialist who claimed that he always adopted a free "peasant" persona when playing online games set in medieval Arthurian England. Peasants would be at a disadvantage in those games, because they'd have limited resources, but players could pay for a more powerful persona (a squire or a knight, for example). Harry boasted that even though he could afford to pay, he was virtuously "handicapping" himself to show solidarity with the working classes throughout the ages. But some of his friends suspected Harry was lying, and that he didn't become a peasant in the virtual world. In fact, Harry was thought to become an earl (some thought maybe he even paid enough to become King Arthur himself! :)