Hi, Davian

Ok . . . I have said some things about who God is and what spiritual is >So, God is "tangible" . . . "experiencible", but in the spiritual realm, in our hearts and minds. But we can limit ourselves, by wanting to relate with material things and pleasures (2 Corinthians 6:12), and such a focus can keep us from testing if and how God exists.
So, in order to test God, we need to deeply be changed by Him so we can share with Him in His love, and submit to how He rules us and cares for us deeply in His own peace. This is part of the basic calling of Christianity, by the way . . . for all of us, and not only for certain special-status, super-spiritual "saints" >
"And let the peace of God rule in your hearts, to which also you were called in one body; and be thankful." (Colossians 3:15)
We test and discover God, by offering ourselves to Him and then obeying how He rules us in His peace . . . discovering so better than we can get with our own self-effort.
And because this thread is about what prayer is for, I will offer part of what I have experienced of prayer >
Every Christian in prayer is sensing for and submitting to how our Father rules us in His peace, or correcting us so we do

Prayer includes submitting to God, for how He corrects us (Hebrews 12:4-11) so then we can obey how He personally shares with and rules each of us His children, in His very own peace.
So, in case certain religious people are trying to use prayer only or mainly to get certain things they want, their approach can in fact be keeping them from all God has for them.
Philippians 4:6-7 says this about what prayer is for >
"Be anxious for nothing, but in everything by prayer and supplication, with thanksgiving, let your requests be made known to God, and the peace of God, which surpasses all understanding, will guard your hearts and minds through Christ Jesus." (Philippians 4:6-7)
So, the only real way to test God is to pray to obey all He does with us.
It is like testing a car, in some way - - - I can't tell you how to test a car or what a car is really like; you need to get in the car and find out!!!
In the spiritual realm there are different beings who are >
But God is greater and better than how humans are, spiritually, and certainly superior to non-human evil beings who are spiritual with no physical bodies > God is >
conscious, "even" having feelings and emotions which are not like those of humans
loving, while incapable of being changed or hurt or overpowered by any evil or pleasures . . . an advantage He is able to share with us, in His love having almighty power of sweetly soothing immunity against sin-sick stuff > worth testing, Davian, to find out how this is
personally communicating with every human, either by personally sharing with us and leading and guiding us, or we are having a run-in with the personal communication of God's resistance > "God resists the proud" (in James 4:6, and also in 1 Peter 5:5);
the Supreme Being of family caring and sharing love.
So, in case any of us goes against God, we in our pride are personally communicating with God's resistance which is caring to help slow us down from getting into as much trouble and tragedy as we could

It is better to trust in Jesus and discover forgiveness and living in His peace

which is deeper and better than any human understanding and physical experiences or how humans are able to do each other good.
"Often enough", we Christians do discover that we are getting into messes of not obeying God in His peace; then is when we need to pray, to seek our Heavenly Father's correction and restoration so we are back with Him in His love and doing what He has us doing in His peace. Prayer includes this seeking of correction when we get into the wrong direction

And God does us so much more good, than what we try to get for ourselves and on our own >
"Because Your lovingkindness is better than life,
.My lips shall praise you." (Psalm 63:3)
So, the only way I myself can test this, Davian, is to trust God and pray for Him to do this with us. And this comes through Jesus; there is no other way; Jesus is the One who left Heaven, itself, because God cares about us; and so Jesus is not conceited, but loves us . . . including enough to so suffer and die for our sins, so we can be reconciled with God and forgiven, then test and discover all He has for us . . . but testing with Him >
"Test all things; hold fast what is good." (1 Thessalonians 5:21)
And this testing for what is good is done by means of prayer > including being open for all that is so better than what we can think to ask for. So, prayer needs to not be limiting us to only dealing with problems we want solved and pleasures we want. God is so greater and better than we are . . . to be discovered by maybe I could say "open" prayer