A testing apparatus, comprising: a testing chamber having an upstream end, a downstream end, a device central axis, and a general flow direction, comprising: a chamber body having an upstream cap, a downstream cap, a first chamber wall, and a second chamber wall, where the first chamber wall has a first diameter and in part defines a first chamber interior, the second chamber wall has a second diameter, the first diameter is less than the second diameter, and both the first chamber wall and the second chamber wall are positioned relative to one another such that an annulus is defined in part in between, where the upstream cap is proximate to and couples with at least the first chamber wall towards the upstream end, where the downstream cap is proximate to and couples with at least the first chamber wall towards the downstream end, where the first chamber wall defines a flow passage such that both a fluid and a lost circulation material, or LCM, may pass from the first chamber interior into the annulus, where the chamber body further defines a chamber interior, which includes the annulus and the first chamber interior, through which the fluid and the LCM may traverse along a fluid flow path that is at least in part aligned with the general flow direction and the device central axis, and where traversal of the fluid and the LCM along the fluid flow path is restricted by a flow restriction; a fluid inlet conduit that is in fluid communication with the first chamber interior and is configured to introduce the fluid into the first chamber interior upstream of the flow passage; an LCM inlet that is in fluid communication with the first chamber interior and is configured to introduce the LCM into the first chamber interior upstream of the flow passage; and a fluid outlet conduit that is in fluid communication with the annulus and is configured for passing both the fluid and the LCM from the annulus downstream of the flow passage. a testing chamber having an upstream end, a downstream end, a device central axis, and a general flow direction, comprising: a chamber body having an upstream cap, a downstream cap, a first chamber wall, and a second chamber wall, where the first chamber wall has a first diameter and in part defines a first chamber interior, the second chamber wall has a second diameter, the first diameter is less than the second diameter, and both the first chamber wall and the second chamber wall are positioned relative to one another such that an annulus is defined in part in between, where the upstream cap is proximate to and couples with at least the first chamber wall towards the upstream end, where the downstream cap is proximate to and couples with at least the first chamber wall towards the downstream end, where the first chamber wall defines a flow passage such that both a fluid and a lost circulation material, or LCM, may pass from the first chamber interior into the annulus, where the chamber body further defines a chamber interior, which includes the annulus and the first chamber interior, through which the fluid and the LCM may traverse along a fluid flow path that is at least in part aligned with the general flow direction and the device central axis, and where traversal of the fluid and the LCM along the fluid flow path is restricted by a flow restriction; where the first chamber wall has a first diameter and in part defines a first chamber interior, the second chamber wall has a second diameter, the first diameter is less than the second diameter, and both the first chamber wall and the second chamber wall are positioned relative to one another such that an annulus is defined in part in between, where the upstream cap is proximate to and couples with at least the first chamber wall towards the upstream end, where the downstream cap is proximate to and couples with at least the first chamber wall towards the downstream end, where the first chamber wall defines a flow passage such that both a fluid and a lost circulation material, or LCM, may pass from the first chamber interior into the annulus, where the chamber body further defines a chamber interior, which includes the annulus and the first chamber interior, through which the fluid and the LCM may traverse along a fluid flow path that is at least in part aligned with the general flow direction and the device central axis, and where traversal of the fluid and the LCM along the fluid flow path is restricted by a flow restriction; a fluid inlet conduit that is in fluid communication with the first chamber interior and is configured to introduce the fluid into the first chamber interior upstream of the flow passage; an LCM inlet that is in fluid communication with the first chamber interior and is configured to introduce the LCM into the first chamber interior upstream of the flow passage; and a fluid outlet conduit that is in fluid communication with the annulus and is configured for passing both the fluid and the LCM from the annulus downstream of the flow passage.