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Course contents

  • How to Use This Puzzle Bank
  • SystemVerilog Language Puzzles25
  • Difficulty Guide
  • Full Topic Map
  • Interview-Day Tips
  • Study Route: One Week Before the Interview
  • Study Route: Two Weeks
  • Study Route: Four Weeks (Full Course)4
  • OOP & Testbench Puzzles25
    • Handle and Copy Puzzles
    • Virtual Method Puzzles
    • Parameterized Class Puzzles
    • Factory Override Puzzles
    • OOP & Testbench Puzzles: Tricky Q&A
  • Concurrency & Timing Puzzles25
  • Randomization & Constraint Puzzles25
  • SVA Assertion Puzzles25
  • Functional Coverage Puzzles25
  • Logic & Aptitude Puzzles25
  • Scenario & Debug Puzzles25
  • UVM Testbench Puzzles25
  • Clock, Reset & CDC Puzzles25
  • Bus and Interface Protocol Puzzles25
  • Interview Prep: Puzzle Rounds7
  • DV Puzzle Cheatsheet
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←OOP & Testbench Puzzles
  1. Topics
  2. DV Interview Puzzles
  3. OOP & Testbench Puzzles
  4. OOP & Testbench Puzzles: Tricky Q&A
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    VLSI DV Interview PuzzlesAll levels

    OOP & Testbench Puzzles: Tricky Q&A

    Rapid-fire interview Q&A for OOP & Testbench Puzzles.

    Section Q&A

    Rapid-fire questions an interviewer asks around OOP & Testbench Puzzles. Answer out loud, then check yourself.

    Q1. In a copy/clone debug session, what is the fastest way to prove nested-handle aliasing instead of scoreboard compare bug?

    Answer: Print `%p` (or object IDs) for the nested handles in source and clone before and after one controlled mutation. If identities match and both values move together, the clone path is shallow at that nesting point.

    Trap: Inspecting only top-level object handles and concluding clone ownership is correct.

    Q2. Why can a perfectly implemented derived method still never run in UVM flows?

    Answer: Because framework code often stores objects/components in base-typed handles. If the base declaration is non-virtual or signatures do not match for override, calls bind to base implementation regardless of runtime type.

    Trap: Believing method-name match in derived class automatically guarantees polymorphic dispatch.

    Q3. How do you intentionally design one counter per `foo#(T)` specialization and another truly global counter?

    Answer: Place per-specialization static members inside the parameterized class, and place global static state in package scope or a non-parameterized base class. Validate by constructing at least two different specializations and checking both counters.

    Trap: Keeping both statics inside `foo#(T)` and expecting one of them to be global across all `T`.

    Q4. When both type and instance overrides exist, what mental model predicts factory result reliably?

    Answer: Resolve each `create()` against its full path (`{context}.{name}`): a matching instance override beats any type override, and among several matching instance overrides the first one registered wins (there is no specificity ranking). With no instance match, the type override applies. Then remember direct `new()` bypasses all of it.

    Trap: Believing an exact path beats a wildcard, omitting the leaf name from the instance path, and forgetting `create` vs `new`.

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    See also

    • Handle and Copy Puzzles
    • Virtual Method Puzzles
    • Parameterized Class Puzzles