add examples test, that is mostly used to demonstrate grc20 functiona…

…lities

examples/gno.land/p/demo/grc/grc20/examples_test.gno

@@ -1,18 +1,124 @@
 package grc20
 
-// XXX: write Examples
-
-func ExampleInit()                            {}
-func ExampleExposeBankForMaketxRunOrImports() {}
-func ExampleCustomTellerImpl()                {}
-func ExampleAllowance()                       {}
-func ExampleRealmBanker()                     {}
-func ExamplePrevRealmBanker()                 {}
-func ExampleAccountBanker()                   {}
-func ExampleTransfer()                        {}
-func ExampleApprove()                         {}
-func ExampleTransferFrom()                    {}
-func ExampleMint()                            {}
-func ExampleBurn()                            {}
+import (
+	"gno.land/p/demo/ufmt"
+	"std"
+)
+
+// ExampleInit demonstrates how to initialize a new token.
+func ExampleInit() {
+	token, ledger := NewToken("ExampleToken", "EXM", 2)
+	ufmt.Println(token.GetName())   // Output: ExampleToken
+	ufmt.Println(token.GetSymbol()) // Output: EXM
+	ufmt.Println(token.GetDecimals()) // Output: 2
+	ufmt.Println(ledger.totalSupply) // Output: 0
+}
+
+// ExampleTransfer demonstrates how to transfer tokens between accounts.
+func ExampleTransfer() {
+	token, ledger := NewToken("ExampleToken", "EXM", 2)
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+	stefan := std.Address("g1dxr7hh6rm3r5wlrkg23qm0fugak3lu8x30kky8")
+
+	ledger.Mint(tony, 1000)
+	ledger.Transfer(tony, stefan, 200)
+
+	ufmt.Println(token.BalanceOf(tony)) // Output: 800
+	ufmt.Println(token.BalanceOf(stefan))   // Output: 200
+}
+
+// ExampleApprove demonstrates how to approve a spender and transfer tokens using allowance.
+func ExampleApprove() {
+	token, ledger := NewToken("ExampleToken", "EXM", 2)
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+	stefan := std.Address("g1dxr7hh6rm3r5wlrkg23qm0fugak3lu8x30kky8")
+	carl := std.Address("carl")
+
+	ledger.Mint(tony, 1000)
+	ledger.Approve(tony, stefan, 300)
+	ledger.TransferFrom(tony, stefan, carl, 200)
+
+	ufmt.Println(token.BalanceOf(tony)) // Output: 800
+	ufmt.Println(token.BalanceOf(carl))  // Output: 200
+	ufmt.Println(token.Allowance(tony, stefan)) // Output: 100
+}
+
+// ExampleMint demonstrates how to mint new tokens.
+func ExampleMint() {
+	token, ledger := NewToken("ExampleToken", "EXM", 2)
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+
+	ledger.Mint(tony, 500)
+
+	ufmt.Println(token.BalanceOf(tony)) // Output: 500
+	ufmt.Println(token.TotalSupply())    // Output: 500
+}
+
+// ExampleBurn demonstrates how to burn tokens.
+func ExampleBurn() {
+	token, ledger := NewToken("ExampleToken", "EXM", 2)
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+
+	ledger.Mint(tony, 500)
+	ledger.Burn(tony, 200)
+
+	ufmt.Println(token.BalanceOf(tony)) // Output: 300
+	ufmt.Println(token.TotalSupply())    // Output: 300
+}
+
+// ExampleCallerTeller demonstrates how to use the CallerTeller.
+func ExampleCallerTeller() {
+	token, _ := NewToken("ExampleToken", "EXM", 2)
+	teller := token.CallerTeller()
+
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+	stefan := std.Address("g1dxr7hh6rm3r5wlrkg23qm0fugak3lu8x30kky8")
+
+	std.TestSetOrigCaller(tony)
+	teller.Approve(stefan, 100)
+
+	ufmt.Println(token.Allowance(tony, stefan)) // Output: 100
+}
+
+// ExampleReadonlyTeller demonstrates how to use the ReadonlyTeller.
+func ExampleReadonlyTeller() {
+	token, _ := NewToken("ExampleToken", "EXM", 2)
+	teller := token.ReadonlyTeller()
+
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+
+	// Attempting to approve should result in an error
+	err := teller.Approve(tony, 100)
+	ufmt.Println(err == ErrReadonly) // Output: true
+}
+
+// ExampleRealmTeller demonstrates how to use the RealmTeller.
+func ExampleRealmTeller() {
+	token, _ := NewToken("ExampleToken", "EXM", 2)
+	teller := token.RealmTeller()
+
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+	stefan := std.Address("g1dxr7hh6rm3r5wlrkg23qm0fugak3lu8x30kky8")
+
+	std.TestSetOrigCaller(tony)
+	teller.Transfer(stefan, 50)
+
+	ufmt.Println(token.BalanceOf(stefan)) // Output: 50
+}
+
+// ExampleImpersonateTeller demonstrates how to use the ImpersonateTeller.
+func ExampleImpersonateTeller() {
+	token, ledger := NewToken("ExampleToken", "EXM", 2)
+	tony := std.Address("g1ej0qca5ptsw9kfr64ey8jvfy9eacga6mpj2z0y")
+	stefan := std.Address("g1dxr7hh6rm3r5wlrkg23qm0fugak3lu8x30kky8")
+
+	ledger.Mint(tony, 1000)
+	teller := ledger.ImpersonateTeller(stefan)
+
+	teller.Transfer(tony, 100)
+
+	ufmt.Println(token.BalanceOf(tony)) // Output: 1100
+	ufmt.Println(token.BalanceOf(stefan))   // Output: 0
+}
 
 // ...