Only in the decisive set did Swiss Hingis move on top of the battling Frenchwoman to score a hard-fought 7-5, 5-7, 6-2 win for a place in the last four of the Berlin clay-court tournament.
``It was a helluva match,'' said Hingis after two hours and 27 minutes of highly entertaining tennis. The defending champion goes on to meet third seed Conchita Martinez, who crushed Gala Leon Garcia 6-4, 6-2 in an all-Spanish affair.
Amanda Coetzer, who dumped local favorite Anke Huber 6-4, 6-4, will take on either fellow South African Joannette Kruger or Russian Elena Dementieva in the other semifinal on Saturday.
Hingis entered her match against fifth seed Testud full of confidence, having won their nine previous encounters.
But the two had never met on clay.
A determined Testud broke her prestigious opponent in the seventh game and served for the first set, only to drop serve by netting a backhand. Hingis later fired a brilliant return winner to claim the set.
The second set was just as tight with both players struggling to hold serve. There were plenty of long, exciting rallies until Testud, who had already served for the set in the ninth game, sealed it with Hingis hitting a forehand wide.
Testud then appeared to get tired and Hingis broke her to open up a 4-2 lead in the third set. She stayed on top until she earned three match points. Testud bowed out with an unforced error on the first.
``Every time I play against her I know it's going to be a tough one,'' Hingis said after a perfect warm-up for the French Open starting on May 29.
``I took too many risks in the first two sets. You have to be patient on clay and I guess I wasn't patient enough. In the end I got a second breath and I was a little smarter.''
Hingis can expect another tough test in the next round against claycourt expert Martinez.
Leon Garcia, who had knocked out two seeded players, Anna Kournikova and Chanda Rubin, on her way to the last eight, resisted Martinez in the first set, which lasted over an hour.
Huber Let Down By Her Serve
Not until the last game of that set did Martinez manage the telling break.
She stepped up a gear in the second set, cruising to a 4-0 lead. Leon Garcia saved one match point in the seventh game but Martinez then served for the match and wrapped it up with her opponent sending a backhand wide.
Huber, under the spotlight as the great German hope in a tournament won nine times by Steffi Graf, put in a brave fight against Coetzer but was let down by her serve, committing many double faults.
``I'm playing well and I have a good chance of making it to the final,'' said number 10 seed Coetzer.
World number 12 Huber, the eighth seed, would have broken back into the top 10 for the first time in over two years had she won.
Both players had dropped serve once when Coetzer broke Huber to lead 5-4 in the first set, which she took in the next game with a forehand volley on set point.
The second set followed a similar scenario. Huber survived two match points before hitting a return long on the third.
``I wasn't on top of my game and when I'm not, I can't win on clay,'' the German said.