You can also get caught by the routing of wires. Consider these 2 schematic segments. They have exactly the same (end point to end point) wire connections. The one of the right though has the bends in each of the wires at exactly the same point in the middle. Both of these are electrically (on schematic) equivalent to the left example above, but the dot for the bend is smaller than the dot for a connection. Making it hard to tell apart from the right diagram above. Where practical, route wires to avoid crossing where there is no connection. That is not always easy (or even possible). You should though always be able to avoid routing wires and bend points directly on top of each other.
For more advanced cases, real wiring like this (on PCB for example) should be avoided. It creates a ‘loop’, which can cause strange effects because the wires are not actually zero resistance.
Uing the “left click”, you can always get Fritzing to show which connectors are actually connected. Where parts have internal connections (bus) defined, that can show things connected where there is no wire in the schematic. For example, there is an invisible wire between the 3 separate ground pins on an Arduino Uno board. That does not show in schematic, but does show on breadboard view. Other parts might have multiple pins in schematic view that are invisibly connected.
