test_that(
  "TRCM remains close to straight and bent cylinder reference problems",
  {
    density_sw <- 1026.8
    sound_speed_sw <- 1477.3
    g_body <- 1.0357
    h_body <- 1.0279
    length_body <- 10.5e-3
    radius_body <- 1e-3
    radius_curvature_ratio <- 1.5
    ka <- seq(0.5, 5, length.out = 12)
    frequency <- ka * sound_speed_sw / (2 * pi * radius_body)

    straight <- fls_generate(
      shape = cylinder(
        length_body = length_body,
        radius_body = radius_body,
        n_segments = 401
      ),
      density_body = density_sw * g_body,
      sound_speed_body = sound_speed_sw * h_body,
      theta_body = pi / 2
    )

    bent <- fls_generate(
      shape = cylinder(
        length_body = length_body,
        radius_body = radius_body,
        radius_curvature_ratio = radius_curvature_ratio,
        n_segments = 401
      ),
      density_body = density_sw * g_body,
      sound_speed_body = sound_speed_sw * h_body,
      theta_body = pi / 2
    )

    straight_fcms <- target_strength(
      straight,
      frequency,
      "FCMS",
      boundary = "liquid_filled",
      density_sw = density_sw,
      sound_speed_sw = sound_speed_sw
    )

    straight_trcm <- target_strength(
      straight,
      frequency,
      "TRCM",
      density_sw = density_sw,
      sound_speed_sw = sound_speed_sw
    )

    bent_trcm_fresnel <- target_strength(
      bent,
      frequency,
      "TRCM",
      density_sw = density_sw,
      sound_speed_sw = sound_speed_sw,
      stationary_phase = FALSE
    )

    bent_trcm_stationary <- target_strength(
      bent,
      frequency,
      "TRCM",
      density_sw = density_sw,
      sound_speed_sw = sound_speed_sw,
      stationary_phase = TRUE
    )

    lebc <- .trcm_equivalent_length_fresnel(
      k1 = 2 * pi * frequency / sound_speed_sw,
      l = length_body,
      a = radius_body,
      rho_c = radius_curvature_ratio * length_body
    )

    bent_reference_ts <- 20 * log10(abs(lebc * straight_fcms@model$FCMS$f_bs /
      length_body))

    expect_lt(
      mean(abs(straight_trcm@model$TRCM$TS - straight_fcms@model$FCMS$TS)),
      1
    )
    expect_lt(
      mean(abs(bent_trcm_fresnel@model$TRCM$TS - bent_reference_ts)),
      1
    )
    expect_lt(
      mean(abs(bent_trcm_stationary@model$TRCM$TS - bent_reference_ts)),
      2
    )
  }
)