Position-size should NEVER be over available_capital

Part of #4353

tests/edge/test_edge.py

@@ -209,7 +209,7 @@ def test_nonexisting_stoploss(mocker, edge_conf):
     assert edge.stoploss('N/O') == -0.1
 
 
-def test_stake_amount(mocker, edge_conf):
+def test_edge_stake_amount(mocker, edge_conf):
     freqtrade = get_patched_freqtradebot(mocker, edge_conf)
     edge = Edge(edge_conf, freqtrade.exchange, freqtrade.strategy)
     mocker.patch('freqtrade.edge.Edge._cached_pairs', mocker.PropertyMock(
@@ -217,20 +217,33 @@ def test_stake_amount(mocker, edge_conf):
             'E/F': PairInfo(-0.02, 0.66, 3.71, 0.50, 1.71, 10, 60),
         }
     ))
-    free = 100
-    total = 100
-    in_trade = 25
-    assert edge.stake_amount('E/F', free, total, in_trade) == 31.25
+    assert edge._capital_ratio == 0.5
+    assert edge.stake_amount('E/F', free_capital=100, total_capital=100,
+                             capital_in_trade=25) == 31.25
 
-    free = 20
-    total = 100
-    in_trade = 25
-    assert edge.stake_amount('E/F', free, total, in_trade) == 20
+    assert edge.stake_amount('E/F', free_capital=20, total_capital=100,
+                             capital_in_trade=25) == 20
 
-    free = 0
-    total = 100
-    in_trade = 25
-    assert edge.stake_amount('E/F', free, total, in_trade) == 0
+    assert edge.stake_amount('E/F', free_capital=0, total_capital=100,
+                             capital_in_trade=25) == 0
+
+    # Test with increased allowed_risk
+    # Result should be no more than allowed capital
+    edge._allowed_risk = 0.4
+    edge._capital_ratio = 0.5
+    assert edge.stake_amount('E/F', free_capital=100, total_capital=100,
+                             capital_in_trade=25) == 62.5
+
+    assert edge.stake_amount('E/F', free_capital=100, total_capital=100,
+                             capital_in_trade=0) == 50
+
+    edge._capital_ratio = 1
+    # Full capital is available
+    assert edge.stake_amount('E/F', free_capital=100, total_capital=100,
+                             capital_in_trade=0) == 100
+    # Full capital is available
+    assert edge.stake_amount('E/F', free_capital=0, total_capital=100,
+                             capital_in_trade=0) == 0
 
 
 def test_nonexisting_stake_amount(mocker, edge_conf):