Wireless Sensor Network (WSN) is strongly affirmed as an indispensable technology that exploits sensor nodes’(SNs’) key abilities (sensing, processing and communication) to achieve limitless remote sensing applications in many fields such as data acquisition in health, smart grid systems, monitoring of dangerous and inaccessible environments, monitoring of critical infrastructures and military operations. Despite these myriad merits, the core of this technology, SNs, are highly vulnerable to faults due to their fragility, resource-constrained nature and the fact that they are mostly deployed in hostile and turbulent environments to operate autonomously without accessibility for maintenance. Since faults and failures are inevitable in WSNs, a clearer relationship between the different types of faults in WSNs, the suitable fault detection (FD) and fault tolerance (FT) techniques for effective fault management (FM) are imperative. Till date, many interesting FD/FT algorithms have been proposed, however, these algorithms are shelved because they are probably not founded on realistic assumptions. This paper presents a systematic review of faults and FD/FT algorithms in the context of the realities and current advances in WSNs. This study in its novelty delves into the relationship between the different types of faults to establish the root causes or root sources of faults in WSNs, assesses the realities of the basic assumptions of existing FD/FT schemes to establish the correlations between the basic assumptions and the realities in WSNs and finally, examines existing FD/FT schemes against some key inherent fault-affinity factors of the SNs. This study recommends that future FD/FT designs should give higher priority to the root-causes of faults in WSNs rather their consequences.