test + example update

Author: vitaliidm

x-pack/plugin/esql/qa/testFixtures/src/main/resources/math.csv-spec

@@ -1713,12 +1713,16 @@ magnitude:double | sign:double | result:double
 ;
 
 copySignOfPositiveToNegative
+// tag::copySign-PosToNeg[]
 ROW magnitude = 5.2, sign = -9.0
 | EVAL result = COPY_SIGN(magnitude, sign)
+// end::copySign-PosToNeg[]
 ;
 
+// tag::copySign-PosToNeg-result[]
 magnitude:double | sign:double | result:double
 5.2              | -9.0        | -5.2
+// end::copySign-PosToNeg-result[]
 ;
 
 copySignOfNegativeToPositive
@@ -1783,3 +1787,11 @@ ROW magnitude = 9223372036854775808, sign = -11.2
 magnitude:unsigned_long | sign:double | result:double
 9223372036854775808     | -11.2       | -9223372036854775808
 ;
+
+copySignAsArgument
+ROW result = SIGNUM(COPY_SIGN(24, -11))
+;
+
+result:double
+-1
+;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/math/CopySign.java

@@ -40,7 +40,7 @@ public class CopySign extends EsqlScalarFunction {
     @FunctionInfo(
         returnType = { "double" },
         description = "Returns the first argument with the sign of the second argument.",
-        examples = @Example(file = "math", tag = "CopySign")
+        examples = @Example(file = "math", tag = "copySign-PosToNeg")
     )
     public CopySign(
         Source source,