There comes a point in understanding circuits where you can look at a schematic and read the intent of the design, and understand its operation. Although the diagram may show an ocean of resistors, capacitors, inductors, transistors, transformers, connectors, etc, you get to the point where you just see the flow and understand the circuit (if it is well-drawn).

Many flaws in circuit design can be spotted by inspection. Your eyes are drawn to problem areas, where things just don't look right. This is not a brute-force calculation. It is similar to chess, where a master sees only a few moves where there are opportunities. This is in contrast to a computer, which plays chess by evaluating myriads of moves.

When you get really advanced, you can even see humor in some schematics, both in the way the diagrams are drawn, the choice of components, and the topology. When someone points and laughs at your schematic, it is not unlike the experience of someone pointing and laughing at your code.

In many ways reading code is harder than writing it. You are good when you can read someone else's code, appreciate what is good about it, and see where it is likely to have problems. This can be done quite quickly and intuitively.

I am much better at reading schematics than reading perl code! There are many great books that help you learn to read code, though. For help reading schematics, the titles are far fewer. 'The Art of Electronics' by Horowitz and Hill is the title that comes to mind for circuits.

Like a well-coded test suite, a very thorough simulation of an electronic design can result in detailed analysis of design flaws. I have found that these thorough simulations must be created by someone who understands the circuit. In other words, black box simulation does not work for the types of analog designs that I look at. This leads me to suspect that software test development is also not best when it designed on a black-box.

The analogies between hardware and software run deep.