test: test borrow caps on create loan

Author: AlbertoCentonze

tests/unitary/controller/test_create_loan.py

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+import boa
+
+from tests.utils.constants import WAD
+
+BORROW_CAP = 10**9
+COLLATERAL = 10**21
+N_BANDS = 5
+
+
+def test_borrow_cap_reverts_when_exceeded(controller, collateral_token):
+    controller.eval(f"core.borrow_cap = {BORROW_CAP}")
+    controller.eval(f"core._total_debt.initial_debt = {BORROW_CAP}")
+    controller.eval(f"core._total_debt.rate_mul = {WAD}")
+
+    boa.deal(collateral_token, boa.env.eoa, COLLATERAL)
+    collateral_token.approve(controller, 2**256 - 1)
+
+    with boa.reverts("Borrow cap exceeded"):
+        controller.create_loan(COLLATERAL, 1, N_BANDS)