update header comment for --reduce-test (#3910)

test/reduce.js

@@ -4,19 +4,17 @@ var List = U.List;
 var os = require("os");
 var sandbox = require("./sandbox");
 
-// Reduce a ufuzz-style `console.log` based test case by iteratively replacing
+// Reduce a test case by iteratively replacing AST nodes with various
-// AST nodes with various permutations. Each AST_Statement in the tree is also
+// permutations. Each AST_Statement in the tree is also speculatively dropped
-// speculatively dropped to determine whether it is needed.  If the altered
+// to determine whether it is needed.  If the altered tree and the last known
-// tree and the last known good tree produce the same non-nil error-free output
+// good tree produce the same output after being run, then the permutation
-// after being run, then the permutation survives to the next generation and
+// survives to the next generation and is the basis for subsequent iterations.
-// is the basis for subsequent iterations.  The test case is reduced as a
+// The test case is reduced as a consequence of complex expressions being
-// consequence of complex expressions being replaced with simpler ones.
+// replaced with simpler ones.  Note that a reduced test case will have
-// This function assumes that the testcase will not result in a parse or
+// different runtime output - it is not functionally equivalent to the
-// runtime Error.  Note that a reduced test case will have different runtime
+// original. The only criteria is that once the generated reduced test case is
-// output - it is not functionally equivalent to the original. The only criteria
+// run without minification, it will produce different output from the code
-// is that once the generated reduced test case is run without minification, it
+// minified with `minify_options`.  Returns a `minify` result object.
-// will produce different output from the code minified with `minify_options`.
-// Returns a `minify` result object with an additonal boolean property `reduced`.
 
 Error.stackTraceLimit = Infinity;
 module.exports = function reduce_test(testcase, minify_options, reduce_options) {