If you pray your salahs regularly and ask for an increase in wealth, but your wealth decreases, is that a test?
How do you increase your rizq(sustenance) and wealth?
but your wealth decreases, is that a test?
No one will have the definitive answer!
It might be, it might not
Allah says in surat ibrahim aya 7:
وَإِذْ تَأَذَّنَ رَبُّكُمْ لَئِن شَكَرْتُمْ لَأَزِيدَنَّكُمْ ۖ وَلَئِن كَفَرْتُمْ إِنَّ عَذَابِي لَشَدِيدٌ
Which translates into:
And [remember] when your Lord proclaimed, 'If you are grateful, I will surely increase you [in favor]; but if you deny, indeed, My punishment is severe.' "
As one might understand, the greatest sources of rizq is being thankful
Answer: In my opinion it doesn't matter if it is a test or not, as long as you are content with what God has given you and you give thanks(both verbally and through actions).
A note on Du'a:
Du'a is often cited as the link between a person and God, because you are asking him directly for your needs both spiritual and worldly. So sincere Du'a and prayer is the way to go. But, as Abdullah Geith had mentioned, giving thanks to God is also a source of increase in rizq and required for the sustenance of this wealth.
I would also like to add that Istighfar is also a major source of increase in material and spiritual wealth.
Allah says in surat Nouh, verse 10:
فَقُلْتُ اسْتَغْفِرُواْ رَبَّكُمْ إِنَّهُ كَانَ غَفَّاراً - يُرْسِلِ السَّمَآءَ عَلَيْكُمْ مُدْرَاراً - وَيُمْدِدْكُمْ بِأَمْوَلٍ وَبَنِينَ وَيَجْعَل لَّكُمْ جَنَّـتٍ وَيَجْعَل لَّكُمْ أَنْهَاراً - مَّا لَكُمْ لاَ تَرْجُونَ لِلَّهِ وَقَاراً
I said (to them): Ask forgiveness from your Lord, verily, He is Oft-Forgiving; - He will send rain to you Midrar - And give you increase in wealth and children, and bestow on you gardens and bestow on you rivers - What is the matter with you, that you do not hope for any Waqar from Allah
Giving thanks to God and Istighfar are not only words but actions too. If you are committing or had committed a sin, you have to repent to god and ask for his forgiveness.