Test: Internal exchange coverage (#1525)

* Test: Internal exchange coverage

* Tests: Rename exchange.TestInstance to Setup

This package function is either going to be imported and used as just exchange.Setup,
or more likely testexch.Setup.
This removes the Stutter of having
internal/testing/exchange.TestInstance which is implicit given the
package path

exchanges/binance/binance_live_test.go

@@ -20,7 +20,7 @@ var mockTests = false
 func TestMain(m *testing.M) {
 
 	b = new(Binance)
-	if err := testexch.TestInstance(b); err != nil {
+	if err := testexch.Setup(b); err != nil {
 		log.Fatal(err)
 	}
 

exchanges/binance/binance_mock_test.go

@@ -21,7 +21,7 @@ func TestMain(m *testing.M) {
 	}
 
 	b = new(Binance)
-	if err := testexch.TestInstance(b); err != nil {
+	if err := testexch.Setup(b); err != nil {
 		log.Fatal(err)
 	}