tests: improve consistency and clarity of test diagnostics

Minor updates to test diagnostics for consistency and readability:
- Corrected an incorrect identifier
- Standardized float formatting

No behavior changes.

Change-Id: I3d3633a7cc487209341ea92101f8c67848212080
GitHub-Last-Rev: b2822e846a
GitHub-Pull-Request: golang/go#77001
Reviewed-on: https://go-review.googlesource.com/c/go/+/732762
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

test/cmplxdivide.go

@@ -35,7 +35,7 @@ func main() {
 				fmt.Printf("BUG\n")
 				bad = true
 			}
-			fmt.Printf("%v/%v: expected %v error; got %v\n", t.f, t.g, t.out, x)
+			fmt.Printf("%v/%v: got %v, want %v\n", t.f, t.g, x, t.out)
 		}
 	}
 	if bad {

test/map.go

@@ -431,7 +431,7 @@ func testbasic() {
 		{
 			_, b := mpTi[apT[i]]
 			if b {
-				panic(fmt.Sprintf("tuple nonexistence decl: mpTi[apt[%d]]", i))
+				panic(fmt.Sprintf("tuple nonexistence decl: mpTi[apT[%d]]", i))
 			}
 			_, b = mpTi[apT[i]]
 			if b {