test: test cases to overwrite Prev*

examples/gno.land/r/x/test_prev/gno.mod

@@ -0,0 +1,8 @@
+module gno.land/r/x/test_prev
+
+require (
+	gno.land/p/demo/grc/grc20 v0.0.0-latest
+	gno.land/p/demo/ufmt v0.0.0-latest
+	gno.land/p/demo/users v0.0.0-latest
+	gno.land/r/demo/users v0.0.0-latest
+)

examples/gno.land/r/x/test_prev/test_prev.gno

@@ -0,0 +1,18 @@
+package test_prev
+
+import (
+	"std"
+
+	pusers "gno.land/p/demo/users"
+	"gno.land/r/demo/foo20"
+)
+
+func DoSomeWithUserBalance() string {
+	caller := std.GetOrigCaller()
+	balance := foo20.BalanceOf(pusers.AddressOrName(caller))
+
+	if balance > 100 {
+		return "rich user"
+	}
+	return "poor user"
+}

examples/gno.land/r/x/test_prev/test_prev_test.gno

@@ -0,0 +1,32 @@
+package test_prev
+
+import (
+	"std"
+	"testing"
+
+	"gno.land/r/demo/foo20"
+)
+
+func TestDoSomeWithUserBalancePoor(t *testing.T) {
+	std.TestSetOrigCaller("g1jg8mtutu9khhfwc4nxmuhcpftf0pajdhfvsqf5")
+	if DoSomeWithUserBalance() != "poor user" {
+		t.Error("expected poor user")
+	}
+}
+
+func TestDoSomeWithUserBalanceRichButPoor(t *testing.T) {
+	std.TestSetOrigCaller("g1jg8mtutu9khhfwc4nxmuhcpftf0pajdhfvsqf5")
+	foo20.Faucet() // foo20 will mint tokens to this realm(std.PrevRealm) not user
+	if DoSomeWithUserBalance() != "poor user" {
+		t.Error("expected poor user")
+	}
+}
+
+func TestDoSomeWithUserBalanceRich(t *testing.T) {
+	std.TestSetPrevAddr("g1jg8mtutu9khhfwc4nxmuhcpftf0pajdhfvsqf5")
+
+	foo20.Faucet() // foo20 will mint tokens to this realm not user
+	if DoSomeWithUserBalance() != "rich user" {
+		t.Error("expected rich user")
+	}
+}

gnovm/tests/stdlibs/std/std.go

@@ -2,10 +2,11 @@ package std
 
 import (
 	"fmt"
-	"github.com/gnolang/gno/gnovm/stdlibs"
 	"strings"
 	"testing"
 
+	"github.com/gnolang/gno/gnovm/stdlibs"
+
 	gno "github.com/gnolang/gno/gnovm/pkg/gnolang"
 	"github.com/gnolang/gno/gnovm/stdlibs/std"
 	"github.com/gnolang/gno/tm2/pkg/crypto"